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Night flushing and thermal mass: maximizing natural ventilation for energy conservation through architectural features

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Night flushing and thermal mass: maximizing natural ventilation for energy conservation through architectural features

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NIGHT FLUSHING AND THERMAL MASS:

MAXIMIZING NATURAL VENTILATION FOR ENERGY
CONSERVATION THROUGH ARCHITECTURAL FEATURES

by

Kenneth A. Griffin

A Thesis Presented to the
FACULTY OF THE USC SCHOOL OF ARCHITECTURE
UNIVERSITY OF SOUTHERN CALIFORNIA
In Partial Fulfillment of the
Requirements for the Degree
MASTER OF BUILDING SCIENCE

May 2010

Copyright 2010 Kenneth A. Griffin
ii

Acknowledgements

I would like to extend my deepest gratitude to my entire thesis committee for
guiding and supporting me through the process of this study. My thesis chair, Professor
Doug Noble, was instrumental in keeping me focused and on track. He aided me in the
structure of my project and the steps that needed to be taken in order to fully develop a
strong thesis. I would also like to thank Professor Marc Schiler, whose expertise in
passive systems helped me to understand and answer questions that I had not
considered. His technical and theoretical support on passive cooling and thermal mass
brought validity to what I was studying.
I would especially like to thank Professor Peter Simmonds and Patrick Wilkinson
of IBE Consulting Engineers. They offered their time, expertise, and their office to help
me in developing and completing my thesis. Professor Simmonds mechanical
engineering knowledge helped me understand the calculations and engineering behind
this project and building technology in general. This project would not have been as
successful without his influence and contributions. Patrick Wilkinson taught me how to
use the simulation tool IES Virtual Environment-Pro; the bulk on this thesis project’s
data was generated through this program.
I would also like to thank all of my professors from the University of Southern
California’s Masters of Building Science program, Professor Karen Kensek, Murray Milne,
and Anders Carlson. All of your classes and teachings helped shape my interests in the
study of building technology.
iii

Table of Contents

Acknowledgements .............................................................................................................. ii

List of Figures ...................................................................................................................... vi

List of Tables ..................................................................................................................... xvi

Abstract ............................................................................................................................ xvii

Chapter One: The Significance of Natural Cooling ............................................................. 1
1.1 Introduction ............................................................................................................ 1
1.2 Building Energy Consumption ................................................................................. 2
1.3 Thermal Comfort ..................................................................................................... 6
1.4 LEED......................................................................................................................... 9
1.5 Natural Ventilation and Passive Cooling ............................................................... 11

Chapter Two: How Night Flushing Works ......................................................................... 15
2.1 What is Night Flushing? ........................................................................................ 15
2.2 The Ideal Climate Zone ......................................................................................... 17
2.3 Benefits of Night Flushing vs. Mechanical Cooling ............................................... 20
2.4 Building Design Features that Enhance Night Flushing ........................................ 23
2.5 Thermal Mass ........................................................................................................ 26
2.6 Disadvantages of Night Flushing ........................................................................... 33
2.7 Hybrid Natural Ventilation Systems ...................................................................... 36
2.8 Previous Night Flushing Studies ............................................................................ 40

Chapter Three: Case Studies ............................................................................................. 48
3.1 Lakeview Terrace Branch Library .......................................................................... 48
3.2 The California Science Center Phase II .................................................................. 58
3.3 Santa Clarita Transit Maintenance Facility ........................................................... 63

Chapter Four: Methodology ............................................................................................ 67
4.1 Hypothesis ............................................................................................................. 69
4.2 Selecting a Simulation Tool ................................................................................... 71
4.3 Building the Revit Model....................................................................................... 76
4.4 Matching IESV VE-Pro to Current Performance .................................................... 78
4.5 Implementing Night Flushing ................................................................................ 80

iv

Chapter Five: Original Building Design and Performance ................................................ 82
5.1 Architectural Construction Documents ................................................................ 82
5.2 HVAC Design Intent ............................................................................................... 84
5.3 EnergyPro Simulation ............................................................................................ 86
5.4 Solar Study ............................................................................................................ 88
5.5 Annual Solar Power Generation ........................................................................... 89

Chapter Six: Current Building Performance ..................................................................... 93
6.1 Energy & Gas Consumption Bills ........................................................................... 93
6.2 Energy Management Systems Controls (EMSC) ................................................... 96
6.3 Sylmar Weather Data ........................................................................................... 98
6.4 Monitoring Outdoor & Indoor Climate Data with HOBO’s ................................ 103

Chapter Seven: Night Flushing Simulation Data & Results ............................................ 106
7.1 Matching IES VE-Pro Model to Current Building Performance .......................... 106
7.2 Building Simulation without Passive or Active Heating or Cooling .................... 116
7.3 Night Flushing Simulation using Current Architectural Features ....................... 118
7.4 Enhancing the Thermal Mass .............................................................................. 124
7.5 Enhancing the Glazing ......................................................................................... 130
7.6 Altering the Operable Window Schedule ........................................................... 135
7.7 Enhancing the Lighting System ........................................................................... 139
7.8 Cooling the Rest of the Library ........................................................................... 142
7.9 Energy Consumption ........................................................................................... 149

Chapter Eight: Lakeview Terrace Library Night Flushing and Energy Analysis ............... 154
8.1 Night Flushing Analysis ....................................................................................... 154
8.1.1 Air Flow Analysis .............................................................................................. 155
8.1.2 Adaptive Comfort Chart ................................................................................... 159
8.2 Energy Comparison ............................................................................................. 164
8.3 Cost Analysis ....................................................................................................... 168

Chapter Nine: Conclusions and Recommendations ....................................................... 172
9.1 Lakeview Terrace Library Assessment ................................................................ 172
9.2 Evaluation of Night Flushing on the Library’s Thermal Comfort ........................ 173
9.3 Potential Concerns .............................................................................................. 176
9.4 Overall Effectiveness of Night Flushing .............................................................. 178
9.5 LEED Post-Occupancy .......................................................................................... 179

Chapter Ten: Areas of Future Research .......................................................................... 183

Bibliography: ................................................................................................................... 186

v

Appendices
Appendix A: Architectural Construction Documents ................................................ 191
Appendix B: HVAC Design Intent ............................................................................... 195
Appendix C: Solar Study Data .................................................................................... 198
Appendix D: EMSC Data............................................................................................. 210
Appendix E: Sylmar Weather Data ............................................................................ 217
Appendix F: Data Logger Temperature and Humidity Data for LVT.......................... 222
Appendix G: Matching IES VE-Pro Model to Current Building Data .......................... 234

vi

List of Figures

Figure 1.2.1 – U.S. Energy Consumption Breakdown ......................................................... 3
(Working Towards 2009)
Figure 1.2.2 – 2006 U.S. Commercial Building Energy Use ................................................. 4
(Energy Efficiency Measures 2009)
Figure 1.5.1 – 2006 U.S. Building Energy Expenditures .................................................... 12
(Building Energy Data Book 2009)
Figure 1.5.2 – Cross Ventilation ........................................................................................ 14
(Light, Air, Space 2008)
Figure 1.5.3 – Stack Ventilation ........................................................................................ 14
(Natural Ventilation Systems 2010)
Figure 2.1.1 – Night Flushing Ventilaiton Paths ................................................................ 17
(Sustainable Design Strategies for Perth 2009)
Figure 2.2.1 – Pychrometric Chart for Climate Zone 12 ................................................... 19
(Milne 2007)
Figure 2.5.1 – Thermal Slab Heat Absorption ................................................................... 27
(Passive Cooling 2008)
Figure 2.5.2 – Storage Mass Time Lag .............................................................................. 29
(Stewart 2009)
Figure 2.5.3 – Thermal Mass Heat Flow Peaks ................................................................. 30
(Buntine 2009)
Figure 2.5.4 – Night Flushing Reduced Interior Temperature .......................................... 31
(Buntine 2009)
Figure 2.7.1 – NightBreeze Ventilation Duct .................................................................... 38
(NightBreeze 2008)
Figure 2.8.1 – Mechanical Night Ventilation Cost Saving in CA for Different Bldgs ......... 42
(Braun 2003)
Figure 2.8.2 – La Roche and Milne Test Cells .................................................................... 44
(La Roche)
Figure 3.1.1 – Lakeview Terrace Library ........................................................................... 49

Figure 3.1.2 – Lakeview Terrace Floor Plan ...................................................................... 49

Figure 3.1.3 – Operable Windows & CMU Thermal Mass ................................................ 50

Figure 3.1.4 – Main Reading Room ................................................................................... 50

Figure 3.1.5 – Natural Shading from 2003 to 2009 .......................................................... 52
(AIA 2004)
Figure 3.1.6 – Operable Window Motor ........................................................................... 53

vii

Figure 3.1.7 – Cooling Tower Detail .................................................................................. 55

Figure 3.1.8 – Cooling Tower Air Flow Diagram ............................................................... 55

Figure 3.1.9 – Cooling Tower Interior ............................................................................... 57

Figure 3.1.10 – Signage forLEED Building Innovation ....................................................... 57

Figure 3.2.1 – California Science Center Phase II Glass Curtain Wall ............................... 59

Figure 3.2.2 – Exposed Thermal Mass Ceiling Slab ........................................................... 59

Figure 3.2.3 – Ice Tank Chillers ......................................................................................... 59

Figure 3.2.4 – CSC Rooftop Air Handler Unit .................................................................... 60

Figure 3.2.5 – CSC Underfloor Air Supply ......................................................................... 60

Figure 3.2.6 – West Wall Concrete Thermal Mass............................................................ 62

Figure 3.3.1 – Transit Maintenance Facility Entrance ...................................................... 63

Figure 3.3.2 – Transit Maintenance Facility Wall Section ................................................. 63

Figure 3.3.3 – Raised Floor System ................................................................................... 64

Figure 4.2.1 – TRNSYS Flow Diagram ................................................................................ 73

Figure 4.3.1 – Revit Exterior Renderings .......................................................................... 77

Figure 4.3.2 – Revit Floor Plan with Specified Zones ........................................................ 77

Figure 4.3.3 – Revit Main Reading Room Renderings ...................................................... 78

Figure 5.1.1 – LVT Main Floor Plan ................................................................................... 83

Figure 5.1.2 – LVT Exterior Wall Section ........................................................................... 83

Figure 5.2.1 – Mechanical Plan ......................................................................................... 85

Figure 5.4.1 – August 1
st
Solar Diagrams .......................................................................... 88

viii

Figure 5.5.1 – Entrance Trellis PV Panels .......................................................................... 89

Figure 6.2.1 – EMSC Fan Coil 3 Data for the Main Reading Room ................................... 98

Figure 6.3.1 – Sylmar, CA Weather Station Location ........................................................ 99

Figure 6.3.2 – 2008 Annual Sylmar Weather Data ......................................................... 100

Figure 6.3.3 – Psychrometric Chart for San Fernando, CA ............................................. 102

Figure 6.3.4 – LVT Exterior Wind Rose ............................................................................ 102

Figure 6.4.1 – Data Logger Placements .......................................................................... 104

Figure 6.4.2 – HOBO Data Logger ................................................................................... 104

Figure 7.1.1 – VE-Pro Model ........................................................................................... 106

Figure 7.1.2 – VE-Pro Floor Plan ..................................................................................... 106

Figure 7.1.3 – LVT Lighting/Occupant Schedule ............................................................. 108

Figure 7.1.4 – Sylmar Site Data ....................................................................................... 110

Figure 7.1.5 – Sylmar Site Weather Data ........................................................................ 110

Figure 7.1.6 – Sun Path Diagram ..................................................................................... 111

Figure 7.1.7 – Shading Analysis ....................................................................................... 111

Figure 7.1.8 – LVT Solar Heat Gain .................................................................................. 111

Figure 7.1.9 – Main Reading Room Cooling Loads ......................................................... 115

Figure 7.2.1 – Air Temperature, Outdoor Dry Bulb Temperature, & Wind Speed ......... 117

Figure 7.2.2 – LVT without Active or Passive Cooling PPD & PMV ................................. 118

Figure 7.3.1 – Operable Window Schedule .................................................................... 119

Figure 7.3.2 – Main Reading Room Tᵢ vs. MRT ................................................................ 120

ix

Figure 7.3.3 – Main Reading Room Peak Tᵢ& Tₒ , MRT, & Natural Ventilation ............... 121

Figure 7.3.4 – Main Reading Room Thermal Mass Conduction Gain ............................. 122

Figure 7.3.5 – Main Reading Room PPD vs. PMV ........................................................... 123

Figure 7.3.6 – Main Reading Room Peak PPD & PMV .................................................... 123

Figure 7.4.1 – New High Density 12” Exterior Concrete Block Wall ............................... 124

Figure 7.4.2 – Main Reading Room w/ Enhanced Thermal Mass Tᵢ vs. MRT.................. 125

Figure 7.4.3 – New Thermal Mass Tᵢ , Peak Tₒ , & MRT .................................................. 126

Figure 7.4.4 – New Thermal Mass Tᵢ , Tₒ , MRT, and Wall Conduction Gain .................. 127

Figure 7.4.5 – New Thermal Mass PPD vs. PMV ............................................................. 128

Figure 7.4.6 – Main Reading Room w/Enhanced Thermal Mass Peak PPD & PMV ....... 129

Figure 7.5.1 – Windows 6 – New Double Pane Low E Glazing Parameters .................... 131

Figure 7.5.2 – Main Reading Room w/ New Glazing Tᵢ , SHG, & Glazing Conduction .... 132

Figure 7.5.3 – Main Reading Room Peak Tᵢ and Tₒ , SHG, & Glazing Conduction ........... 133

Figure 7.5.4 – Main Reading Room PPD vs. PMV ........................................................... 134

Figure 7.5.5 – Main Reading Room Peak PPD & PMV .................................................... 134

Figure 7.6.1 – Interior Temperature vs. PPD for New Operable Schedule ..................... 135

Figure 7.6.2– Tᵢ w/out Night Flushing vs. Tₒ ................................................................... 135

Figure 7.6.3– Operable Window Control Conditions ...................................................... 137

Figure 7.6.4– Peak Tᵢ w/Night Flushing vs. Tᵢ w/out Night Flushing ............................... 138

Figure 7.6.5– Tᵢ w/Night Flushing Schedule vs. Tₒ .......................................................... 138

Figure 7.7.1 – Internal Gains ........................................................................................... 140

x

Figure 7.7.2 – Interior Air Temperature with Enhanced Lighting ................................... 140

Figure 7.7.3 – Light Energy Consumption ....................................................................... 141

Figure 7.8.1 – Lobby Night Flushing Tᵢ ............................................................................ 142

Figure 7.8.2 – Lobby Night Flushing PPD vs. PMV .......................................................... 143

Figure 7.8.3 – Main Restroom Tᵢ , PPD, & PMV .............................................................. 143

Figure 7.8.4 – Main Bookstacks Tᵢ , PPD, & PMV ............................................................ 144

Figure 7.8.5 – Multi-Purpose Room Tᵢ ............................................................................ 145

Figure 7.8.6 – Multi-Purpose Room Tᵢ ............................................................................ 145

Figure 7.8.7 – VE-Pro Fan Coil System ............................................................................ 148

Figure 7.8.8 – Heating & Cooling w/ New HVAC & Night Flushing ................................. 148

Figure 7.8.9 – Tᵢ w/ New HVAC & Night Flushing ............................................................ 149

Figure 7.9.1 – Energy Consumption Breakdown ............................................................ 151

Figure 7.9.2 – Total Natural Gas vs. Total Electricity ...................................................... 151

Figure 7.9.3 – Total System Carbon Emissions ............................................................... 153

Figure 8.1.1 – Main Reading Room Air Flow Diagram .................................................... 156

Figure 8.1.2 – Main Reading Room Volumetric Flow .................................................... 157

Figure 8.1.3 – Night Flushing Interior Air Flow ............................................................... 158

Figure 8.1.4 – Night Flushing Exterior Air Flow............................................................... 159

Figure 8.1.5 – June Adaptive Comfort Chart................................................................... 160

Figure 8.1.6 – July Adaptive Comfort Chart .................................................................... 161

Figure 8.1.7 – August Adaptive Comfort Chart ............................................................... 162

xi

Figure 8.1.8 – September Adaptive Comfort Chart ........................................................ 163

Figure 8.2.1 – Energy Comparison .................................................................................. 165

Figure 8.2.2 – Energy Breakdown Comparison ............................................................... 167

Figure 8.3.1 – Annual Cost Comparison .......................................................................... 169

Figure 8.3.2 – Annual Cost Comparison of Equipment & Construction ......................... 170

Figure 9.2.1 – Main Reading Room Tᵢ & PPD .................................................................. 176

Figure A.1 – LVT Floor Plan ............................................................................................. 191

Figure A.2 – LVT Roof Plan .............................................................................................. 191

Figure A.3 – LVT West Elevation ..................................................................................... 192

Figure A.4 – LVT South Elevation .................................................................................... 192

Figure A.5 – LVT East Elevation ....................................................................................... 192

Figure A.6 – LVT North Elevation .................................................................................... 192

Figure A.7 – LVT Section A-A ........................................................................................... 193

Figure A.8 – LVT Section B-B ........................................................................................... 193

Figure A.9 – LVT Section C-C ........................................................................................... 193

Figure A.10 – LVT Section D-D ........................................................................................ 194

Figure A.11 – LVT Section E-E ......................................................................................... 194

Figure A.12 – LVT Exterior Wall Section .......................................................................... 194

Figure B.1 – Mechanical Plan .......................................................................................... 195

Figure B.2 – Chiller Schedule .......................................................................................... 195

Figure B.3 – Hot Water Boiler Schedule ......................................................................... 195

xii

Figure B.4 – Cooling Tower Evaporation Unit Schedule ................................................. 196

Figure B.5 – Fan Coil Schedule ........................................................................................ 196

Figure B.6 – Main Reading Room Fan Coil Control Diagram .......................................... 197

Figure B.7 – Pump Schedule ........................................................................................... 197

Figure C.1 – January 1
st
Solar Diagrams .......................................................................... 198

Figure C.2 – February 1st Solar Diagrams ....................................................................... 199

Figure C.3 – March 1st Solar Diagrams ........................................................................... 200

Figure C.4 – April 1st Solar Diagrams .............................................................................. 201

Figure C.5 – May 1st Solar Diagrams .............................................................................. 202

Figure C.6 – June 1st Solar Diagrams .............................................................................. 203

Figure C.7 – July 1st Solar Diagrams ............................................................................... 204

Figure C.8 – August 1st Solar Diagrams .......................................................................... 205

Figure C.9 – September 1st Solar Diagrams.................................................................... 206

Figure C.10 – October 1st Solar Diagrams ...................................................................... 207

Figure C.11 – November 1st Solar Diagrams .................................................................. 208

Figure C.12 – December1st Solar Diagrams.................................................................... 209

Figure D.1 – EMSC Boiler Data ........................................................................................ 210

Figure D.2 – EMSC Chiller Data ....................................................................................... 210

Figure D.3 – EMSC Cooling Tower Data .......................................................................... 211

Figure D.4 – EMSC Fan Coil 1 Data .................................................................................. 211

Figure D.5 – EMSC Fan Coil 2 Data .................................................................................. 212

xiii

Figure D.6 – EMSC Fan Coil 3 Data .................................................................................. 212

Figure D.7 – EMSC Fan Coil 4 Data .................................................................................. 213

Figure D.8 – EMSC Fan Coil 5 Data .................................................................................. 213

Figure D.9 – EMSC Fan Coil 6 Data .................................................................................. 214

Figure D.10 – EMSC Fan Coil 7 Data ................................................................................ 214

Figure D.11 – EMSC Fan Coil 8 Data ................................................................................ 215

Figure D.12 – EMSC Fan Coil 9 Data ................................................................................ 215

Figure D.13 – EMSC Chiller Schedule .............................................................................. 216

Figure D.14 – EMSC Master Schedule ............................................................................. 216

Figure E.1 – 2009 Annual Sylmar Weather Data............................................................. 217

Figure E.2 – June 2009 Sylmar Weather Data................................................................. 218

Figure E.3 – July 2009 Sylmar Weather Data .................................................................. 219

Figure E.4 – August 2009 Sylmar Weather Data ............................................................. 220

Figure E.5 – September 2009 Sylmar Weather Data ...................................................... 221

Figure F.1 – HOBO 1 ........................................................................................................ 222

Figure F.2 – HOBO 2 ........................................................................................................ 223

Figure F.3 – HOBO 3 ........................................................................................................ 224

Figure F.4 – HOBO 4 ........................................................................................................ 225

Figure F.5 – HOBO 5 ........................................................................................................ 226

Figure F.6 – HOBO 6 ........................................................................................................ 227

Figure F.7 – HOBO 7 ........................................................................................................ 228

xiv

Figure F.8 – HOBO 8 ........................................................................................................ 229

Figure F.9 – HOBO 9 ........................................................................................................ 230

Figure F.10 – HOBO 10 .................................................................................................... 231

Figure F.11 – HOBO 11 .................................................................................................... 232

Figure F.12 – HOBO 12 .................................................................................................... 233

Figure G.1 – FC-1 Cooling Load ....................................................................................... 234

Figure G.2 – FC-2 Cooling Load ....................................................................................... 235

Figure G.3 – FC-3 Cooling Load ....................................................................................... 236

Figure G.4 – FC-4 Cooling Load ....................................................................................... 237

Figure G.5 – FC-5 Cooling Load ....................................................................................... 238

Figure G.6 – FC-6 Cooling Load ....................................................................................... 239

Figure G.7 – Main Bookstacks Cooling Load .................................................................. 239

Figure G.8 – Electrical Room Cooling Load ..................................................................... 240

Figure G.9 – Mechanical Room Cooling Load ................................................................. 240

Figure G.10 – FC-7 Cooling Load ..................................................................................... 241

Figure G.11 – Staff Workroom Cooling Load .................................................................. 241

Figure G.12 – Staff Lounge Cooling Load ........................................................................ 242

Figure G.13 – Head Librarian Office Cooling Load .......................................................... 242

Figure G.14 – I.T. Room Cooling Load ............................................................................. 243

Figure G.15 – Custodial Room Cooling Load ................................................................... 243

Figure G.16 – Staff Storage Room Cooling Load ............................................................. 244

xv

Figure G.17 – Staff Restroom Cooling Load .................................................................... 244

Figure G.18 – FC-8 Cooling Load ..................................................................................... 245

Figure G.19 – Multi-Purpose Room Cooling Load ........................................................... 245

Figure G.20 – Lobby Cooling Load................................................................................... 246

Figure G.21 – Main Restroom Cooling Load ................................................................... 246

Figure G.22 – Cooling Tower Cooling Load ..................................................................... 247

Figure G.23 – Lobby Storage Cooling Load ..................................................................... 247

xvi

List of Tables
Table 1.2.1 – 2006 U.S. Building Energy Consumption ....................................................... 5
(Buildings Energy Data Book 2009)
Table 1.4.1 – LEED Credit Chart for Natural Ventilation and Cooling ............................... 10
(What are the Key Concepts of a Natural Ventilation and Cooling System)
Table 2.4.1 – Latent Thermal Storage Mass Materials ..................................................... 24
(Stewart 2009)
Table 4.2.1 – EnergyPro Totals for Parametric Thermal Mass Tests ................................ 74

Table 5.3.1 – LVT EnergyPro Annual Site Energy Use ....................................................... 87

Table 5.3.2 – LVT EnergyPro Energy Totals ....................................................................... 87

Table 5.5.1 – Solar Panel Data for Rooftop PVC’s ............................................................. 90

Table 5.5.2 – Solar Power Data for Trellis PVC’s ............................................................... 91

Table 6.1.1 – LVT 2008 Electricity Consumption Bill ......................................................... 94

Table 6.1.2 – LVT 2008 Gas Consumption Bill .................................................................. 95

Table 6.1.3 – LVT 2008 Energy Totals ............................................................................... 96

Table 6.3.1 – 2008 Annual Sylmar Weather Data ............................................................. 99

Table 7.1.1 – Thermal Conditions ................................................................................... 109

Table 7.1.2 – Weather Source Comparison .................................................................... 112

Table 7.1.3 – Cooling Loads Comparison ........................................................................ 114

Table 7.8.1 – New Cooling and Heating Loads ............................................................... 147

Table 7.9.1 – Monthly Energy Summary ......................................................................... 150

Table 7.9.2 – LVT Night Flushing Energy Totals .............................................................. 152

Table 7.9.3 –Monthly Carbon Emissions ........................................................................ 153

Table 8.1 – Occupied Hours Environmental Comfort ..................................................... 155

xvii

Abstract

The goals of implementing natural cooling strategies are to reduce a building’s
energy consumption, to improve the indoor climate, and to preserve natural resources.
Energy preservation and sustainable design are beneficial for the building, its occupants,
and the environment. When the passive technique of night flushing is used correctly
with the appropriate architectural features, it can greatly reduce or eliminate the need
for air conditioning and reduce peak energy demands. To test the efficiency of night
flushing and to demonstrate its energy impact and its effect on building performance,
the Lakeview Terrace library was chosen as a case study for modeling night flushing. The
library is advertised as using night flushing for natural ventilation, but after investigating
these claims it was discovered that the library was never designed to night flush. For this
research, the library was modeled for night flushing in IES VE-Pro. After the building was
modeled, its architectural features were altered to maximize energy efficiency by using
night flushing. The simulations show the importance of internal and solar heat gain, as
well as the role all of the building’s features play in natural ventilation. The results of
this study demonstrated that the library redesigned with night flushing could drastically
decrease its energy consumption while maintaining a comfortable indoor climate. It
demonstrated that if the library would have been designed to naturally ventilate using
night flushing, it could have greatly reduced the amount of energy needed for cooling as
well as the cost to power its mechanical system. Night flushing offers an energy
efficient alternative to HVAC without affecting the occupants’ comfort level.
1

Chapter 1: The Significance of Natural Cooling
1.1 - Introduction
The use of mechanical systems (heating / ventilation / air-conditioning - HVAC)
consumes the highest percentage of a building’s total energy demand (Energy Efficiency
Measures 2009). Natural cooling is often overlooked in favor of mechanical cooling
strategies such as air conditioners and air handler units. A passive cooling strategy that
is often underutilized is night flushing with thermal mass. Natural cooling strategies like
night flushing can help to reduce the amount of total energy consumption consumed by
mechanical cooling. The result is a more energy efficient building with a reduced carbon
footprint that can still maintain a comfortable indoor environment. This study’s focus
and interests are on how effective night flushing is and how much more effective it can
be without the need for mechanical fans. It looks to investigate construction with
thermal mass and how to maximize its specific heat capacity. The study will also explore
the use of architectural features to enhance outdoor and interior wind flow and to
reduce external and internal heat gain. Night flushing is ideal in climate zones similar to
that of Southern California, so all of the case studies that have been chosen are from
this region of California. By investigating these aspects, attention will be brought to a
passive cooling strategy that has tremendous potential to make a substantial difference
in a building’s energy consumption and carbon footprint. Before the strategy of night
flushing can be tested and simulated in a building, it is important to first understand
how and why natural ventilation is so important to the building landscape.
2

1.2 - Building Energy Consumption
The rapidly increasing world energy consumption has already raised concerns
over difficulties in the energy supply process, exhaustion of fossil fuels, and heavy
environmental impacts such as ozone layer depletion, creation of excessive levels of
CO
2
, and climate change from global warming,. In 2008 the total United States energy
consumption was 99,304 trillion BTU’s according to the U.S. Department of Energy,
40,178 trillion BTU’s of that total were consumed by buildings (Annual Energy Review
2008). The building sector is broken down into two categories, commercial and
residential. The commercial energy consumption total for 2008 was 18,541 trillion
BTU’s, and the residential energy consumption total was 21,637 trillion BTU’s (Annual
Energy Review 2008). Buildings in the United States as of 2009 consume 72% of
electricity produced, and 55% of U.S. natural gas; they account for about 40% of total
U.S. energy consumption as shown in Figure 1.2.1, costing $350 billion per year
(Working Toward 2009). The worldwide energy consumption from the building sector,
both residential and commercial, has progressively increased, reaching numbers
between 20% and 40% in developed countries like the United States, and has surpassed
the energy consumption generated by the industrial and transportation sectors (Perez-
Lombard 2007). Growing population and the constant demand and acceptance of
mechanical heating and cooling for thermal comfort assure that the trend in energy
consumption will steadily continue to increase.
3

Building energy efficiency is a main objective for energy policy at local, national,
and global levels. The growing rate of energy use from heating, ventilation, and air
conditioning is influencing the energy totals of all of the building services (Perez-
Lombard 2007). The International Energy Agency has compiled alarming data on energy

Figure 1.2.1 – U.S. Energy Consumption Breakdown
trends. During the last two decades, 1984–2004, primary energy has grown by 49% and
CO2 emissions by 43%, with an average annual increase of 2% and 1.8% respectively
(Perez-Lombard 2007).The recent trends in going green and designing for energy
efficiency will hopefully reduce this annual increase.
The residential and commercial building sectors consume 38% of the energy
used in the United States as of 2008 (Energy Consumption 2008). Commercial energy is
used to heat and cool buildings, to provide electricity for lighting, and to operate
appliances and office equipment. The ability to sustain preferred temperatures is one of
the most important aspects of building design. Keeping the living and working spaces at
4

comfortable temperature levels provides a healthier living environment, and it comes at
the price of large amounts of energy consumption. Half of the average building’s energy
consumption comes from heating and cooling (Energy Consumption 2008). The heating,
ventilation and cooling loads of typical commercial office spaces can range between 30-
50% of the total energy load of the building, but on average the total energy is around
32% as shown in Figure 1.2.2. However, this figure is highly unpredictable due to the
high variability in building design, the climate in which they are built, and their quality
(Osburn 2009). According to the U.S. Department of Energy, a building’s HVAC energy

Figure 1.2.2 – 2006 U.S. Commercial Building Energy Use

of heating using about 19.8 % of a buildings total energy and cooling using up 17.7 % as
shown in Table 1.2.1 (Building Energy Data Book 2009). Electricity is the dominant
energy type in residential and commercial buildings as shown in Figure 1.2.3. It provides
5

almost all of the energy used for air conditioning. The efficiency of air conditioners has
increased more than 50 % in the last 25 years. Air conditioners used to average a
Seasonal Energy Efficiency Rating (SEER) of 7 and can now reach a average SEER of 11,
and high efficiency systems can peak at a SEER of 18 (Energy Consumption 2008). “The
use of air conditioners has a serious impact on electricity demand.

Table 1.2.1 – 2006 U.S. Building Energy Consumption

Air conditioning increases peak electricity demand and forces utilities to build
additional power plants to satisfy increasing needs. As reported by Waide (2006): Air
conditioning is already responsible for over half of peak power demand in many regions
of Japan, the United States, and Australia, while its contribution to peak is growing
everywhere (Santamouris 2007).” The increase in peak electricity demand from air
conditioning is a result of cool air being needed during the peak electrical hours of a
building from noon to 2 pm.
6

The goal of a building should be to use natural sources such as wind and sunlight
to operate a building, and then to use mechanical systems when natural cannot be
effective. One way buildings in the United States attempt to conserve energy is by
designing to achieve LEED certification. Energy consumption should be more than a
target needed to receive an award that represents a brand name or a status symbol.
Energy consumption works hand in hand with the amount of greenhouse gas released in
a building; conservation of both is what is needed to ensure a healthier indoor
environment.

1.3 - Thermal Comfort
One of the main goals of a natural ventilation strategy like night flushing is to
achieve thermal comfort. Thermal comfort is determined by indoor and outdoor air
temperature, humidity, airflow, velocity, mean radiant temperature, clothing, and
activity level. “The American Society of Heating, Refrigeration, and Air-conditioning
Engineers (ASHRAE) and the International Standards Organization (ISO) have defined
narrow allowable ranges of temperature and humidity for various building types.
Although these ranges were developed for centrally controlled, air-conditioned
buildings, it is often assumed that they should apply to naturally ventilated buildings as
well. In naturally ventilated buildings occupants are comfortable in a wider range of
temperature and humidity conditions (Malin 2009).” Thermal comfort takes into
account an occupants’ thermal demand which can be determined by location. Comfort
7

levels in Florida are much different than those in California. Temperature and humidity
are both important variables in determining the comfort level of a person in a building.
Buildings need to be designed to conform to what the occupants of the building are
doing. Thermal comfort is ideally met when no one notices the heating or cooling
system whether it is natural or mechanical.
While it is significant that building occupants should have control over a
building’s thermal environment, limitations should be put into place to ensure proper
and efficient operation. The majority of people will be comfortable in the temperature
range between 70°F and 79°F at a humidity ratio of air of 0.004 lbs of water vapor per
lbs of dry air (Osburn 2009). The humidity ratio is the relation between the actual mass
of water vapor present in moist air to the mass of the dry air (The Humidity Ratio of Air
2005). The temperature at which an individual is comfortable is also dependent on
individual occupant factors such as a person’s mass, metabolism, and activity. Since
everyone’s comfort level is different, it is not feasible to design for every person
individually. Clothing can be adjusted to reach a desired comfort range. Sensible people
will put on a sweater if they are cold, or if they are hot they will wear lighter clothing.
The thermal comfort of a building’s occupants and the methods they choose to achieve
it are what dictates the indoor building environment.
Occupants demand a high quality indoor environment in which the building’s
thermal comfort and thermal sensation are taken into account at all times. “A person’s
thermal sensation is essentially related to the thermal balance of the body as a whole.
8

This concept of thermal balance is referred to as thermal neutrality (Simmonds
1991).”This balance is influenced by the comfort variables mentioned before and also by
environmental parameters. “For comfort to be achieved there must also be an absence
of local body thermal discomfort caused by local convective cooling, vertical air
temperature gradients, or asymmetric thermal radiation (Simmonds 1991).”When these
factors have been estimated or measured, the thermal sensation for the body as a
whole can be predicted by calculating the predicted mean vote (PMV).“PMV establishes
a thermal strain based on steady-state heat transfer between the body and the
environment and assigns a comfort vote to that amount of strain. It is impossible to
satisfy all persons in a large group in the same climate. Even with a perfect
environmental system, a predicted percentage of dissatisfied people (PPV) of less than
5% is unattainable (Simmonds 1991).”The desired thermal comfort for occupants in a
building is designed based upon the PPD and PMV levels of the ASHRAE fundamentals.
They are the two main variables for determining the overall occupant comfort level for a
space.

9

1.4–LEED
When evaluating a natural system such as night flushing it is important to
understand what the United States is actively pursuing in terms of green building
strategies. The Leadership in Energy and Environmental Design (LEED) green building
rating system as defined by the U.S. Green Building Council is a system that evaluates
environmental performance from a whole building perspective over a building’s life
cycle, providing a definitive standard for what constitutes a green building in design,
construction, and operation. Buildings that achieve LEED certification are supposed to
utilize resources more efficiently and effectively than regular buildings. The way to
improve the overall quality of a building’s indoor environment and its occupant’s
experience is to achieve the highest level of sustainable design. LEED’s rating is based
on improving the relationship between a building and the environment by reducing the
negative impact a building may have on the natural world. Energy conservation is a goal
that LEED is constantly seeking to obtain; it is one of the main goals it strives to achieve.
Strategies like natural ventilation and cooling are techniques and categories that play an
important role in achieving LEED certification. For LEED-New Construction certification,
natural ventilation and cooling are taken into account in no less than eleven of the
prerequisites and credits. Table 1.4.1 summarizes the impact of a naturally ventilated
and cooled building with respect to the LEED-NC 2.2 rating system.
As of today, LEED is the best available tool in the United States for evaluating a
building’s intent to be environmentally responsible through its design. While it has its
10

LEED-NC 2.2 Credit by Credit Impact of Naturally Ventilated and Cooled Buildings
LEED-NC 2.2 Credit Impact Considerations Notes
Energy & Atmosphere -
EA Prereq. 2 -
Minimum Energy Performance
Major
Impact
Significant influence on
the overall energy
consumption

Energy & Atmosphere -
EA Prereq. 3 -
Fundamental Refrig.
Management
Major
Impact
No refrigerant required
for system
Hybrid system will likely
require refrigerant. Be
sure to select CFC free
options
Energy & Atmosphere -
EA Credit 1 -
Optimize Energy Performance
(worth up to 10 points.)
Major
Impact
Significant influence on
the overall energy
consumption of the
building
ASHRAE 90.1 2004
requires that energy
model include mechanical
cooling, so full energy
savings may not be
credited
Energy & Atmosphere -
EA Credit 4 -
Enhanced Refrig. Management
Major
Impact
No refrigerant required
for system
A hybrid system will likely
require refrigerant. Be
sure to select appropriate
options
Indoor Environmental Quality -
EQ Prereq 1-
Minimum IAQ Performance
Major
Impact
Design to standards in
ASHRAE 62.1-2004
Section 5.1

Indoor Environmental Quality -
EQ Credit 1-
Outdoor Air Delivery Monitoring
Major
Impact
Requires CO2 sensors in
occupied spaces
Credit easier to achieve
with natural ventilation
compared to mechanical.
Indoor Environmental Quality -
EQ Credit 2-
Increased Ventilation
Major
Impact
Follow path described in
Carbon Trust Good
Practice Guide & CIBSE
App Manual 10
Thermal modeling air
flows can be used to
demonstrate ventilation
effectiveness.
Indoor Environmental Quality -
EQ Credit 6.2-
Controllability of Systems:
Thermal Comfort
Major
Impact
Operable windows can
be used in lieu of climate
controls for nearby
occupants
Typically easier to achieve
with natural ventilation
instead of mechanical
ventilation
Indoor Environmental Quality -
EQ Credit 7.1-
Thermal Comfort
Major
Impact
Design to ASHRAE 55-
2004 Section 6.1.1
Standards
Typically difficult to
achieve with natural
ventilation than with
mechanical. Hybrid
systems must comply with
standards for mechanical.
Indoor Environmental Quality -
EQ Credit 8.1 -
Daylight and Views:
Daylight 75% of Spaces
Minor
Impact
Location of operable
windows in project may
benefit daylighting
May be easier to achieve
due to having windows.
Indoor Environmental Quality -
EQ Credit 8.2 -
Daylight and Views:
Views for 90% of Spaces
Minor
Impact
Location of operable
windows in project may
benefit occupant views
May be easier to achieve
due to having windows.
Table 1.4.1 - LEED Credit Chart for Natural Ventilation and Cooling
11

flaws in the area of post-occupancy testing, it has allowed the building industry to make
significant strides towards a more energy efficient and carbon neutral building world.
Just eleven or twelve years ago LEED did not even exist, and now today buildings are
routinely attempting to achieve LEED certification. The reasons behind the building
industries mad push for LEED certification is still a large debate, but the results have led
to a strong movement towards a healthier indoor environment that now cares about
energy consumption, carbon emissions, natural materials, and a healthier indoor
environment.

1.5 - Natural Ventilation and Passive Cooling
If the state of California is to reduce building energy consumption in half by the
year 2010, one key strategy is to design and build buildings to meet the occupant’s
desired comfort level without the use of air conditioning. Air conditioning is very
energy intensive, and it consumes a large portion of a building’s energy bills as shown in
Figure 1.5.1. Today, the use of refrigerated air conditioning is seen as a necessity to a
comfortable environment, regardless of the local climate. Throughout California, even
in the hottest of climates, the implementation of passive design strategies such as
natural ventilation and passive cooling can assist mechanical strategies in keeping
buildings cool, offering substantial first cost savings, and reducing long term operating
costs and energy consumption (Affordable Energy News 2008). Passive cooling offers
the ability to greatly reduce a building’s electrical energy consumption, and thus reduce
12

its total electrical bill. Passive design also incorporates ideas of reducing internal heat
gain as well as solar heat gain, which also will reduce the building’s energy consumption
and electrical costs. Overall natural ventilation is a great strategy for cooling an indoor
environment, but its most positive influence on a property owner is its ability to reduce
a building’s total energy costs.

Figure 1.5.1 – 2006 Building Energy Expenditures
Natural ventilation and passive cooling systems combine intelligent building
design, appropriate climatic conditions, and natural air movement to provide a
building's occupants with fresh air and comfortable conditions without the use of fans
or mechanical air conditioning. Natural ventilation is most successful in moderate
climates such as California and with certain building types. “A combination of climate
and function determines when passive ventilation is doable," says Alisdair McGregor, a
specialist in natural ventilation with Ove Arup & Partners in San Francisco. For example,
13

coastal California, Oregon, and Washington are climatically appropriate if the building is
not too big and internal and if solar gains are not too high (Malin 2009).”Although
coastal California, Oregon, and Washington were specifically listed, natural ventilation
may be possible in other areas. The specific climate is the first area that must be
evaluated when determining what type of natural ventilation is possible, if it even is.
After the climate has been studied, then a building can be designed to maximize the
type of passive system that would be most effective.
The design of a building also directly affects its ability to naturally ventilate. The
buildings’ geometry plays a major role in how much air can be funneled into a building
and what that airflow’s velocity is. An ideal building configuration for natural ventilation
is designed with open floor plans that have a thin depth and have operable windows
that the occupants can easily operate. Desks are a maximum of 23 to 26 feet from a
window. Erik Ring, a researcher at the University of California in Berkeley, says naturally
ventilated spaces typically only have a plan depth of 40 to 50 feet, quite a bit narrower
than most modern commercial buildings (Malin 2009).“Other techniques to boost
cooling include building orientation in relation to the path of the sun and the wind;
facade design, including the use of balconies, windows, and air intakes; solar protection,
including sunshades and other solar-deflection devices; use of passive lighting, such as
skylights, which saves energy and lowers internal heat gain; vegetation and landscaping
to provide shade; and the color of the building (Malin 2009).”
14

Natural ventilation at its simplest form is opening windows and letting in cool air,
but it can also be engineering airflow to bring into the building through the use of wind,
temperature differences and convection, buoyancy, or mechanical fans. Types of
natural ventilation that use this type of manipulated air flow are wind driven cross
ventilation (Figure 1.5.2), stack ventilation (Figure 1.5.3), and night flushing. All of these
strategies use the movement of air to introduce cool air to a space and at the same time
remove hot and stale air. Natural ventilation and passive cooling can also be combined
with mechanical HVAC systems to work in unison, in what is called a mixed mode
system. Buildings that rely on natural ventilation may be more expensive at first and
have a high payback period, due to the higher costs of operable windows and solar
controls. But this is balanced out by avoiding the cost of operating mechanical
ventilation equipment and the energy it consumes. If the building system is mixed
mode, then construction cost tend to be higher, but the system is more effective.

Figure 1.5.2 – Cross Ventilation Figure 1.5.3 – Stack Ventilation
15

Chapter 2: Introduction to the Aspects of Night Flushing

2.1 - What is Passive Night Flushing?
The basis of night flushing without mechanical assistance, like all natural
ventilation principles, is based upon the philosophy of ensuring a fresh and comfortable
indoor climate. This is done with the use of passive cooling and minimal energy
consumption, and at the same time achieving a low cost of operation (Night Cooling
2009). Night flushing’s main function is flushing heat out of a building with cool
nighttime air. The cool nighttime air is circulated throughout the building, thereby
cooling (removing heat from) the building fabric or the interior thermal mass surfaces
such as walls, concrete floors, and furniture (NightBreeze 2008).
The exposed high thermal mass surfaces store heat during the day and release it
at night as the cooler air circulates through the building. The principles of thermal mass
are based on the theories of heat transfer between the entering night time air and the
surface of the thermal mass. Buildings with more thermally massive walls and floors
store the cool night time “coolth” more effectively. “A building with sufficient thermal
mass, which can be exposed to nighttime ventilation, can reduce peak daytime
temperatures by 2° to 3° using this strategy (Free Night Cooling 2009). “During the
nighttime, windows are opened to ventilate a building with cool night outdoor air, both
to obtain natural cooling and to remove stale air. The lower the temperature the
building reaches at night, the longer it will maintain a comfortable temperature
throughout the day. In the morning, windows are closed and the cool surfaces absorb
16

heat throughout the day, keeping indoor temperatures more comfortable and the
building cooler throughout the day. The more coolth the mass can store the longer the
mass can absorb heat the next day, keeping the building cooler for a longer range of
time.
An important factor in night flushing is disposing of the hot stale air that
accumulates in a building throughout the day. One method is by having a building
achieve a negative pressure on each floor so that air can be drawn in through windows
on the lower floors and the hot air can exit through high-level windows in an atrium
using the stack effect as shown in Figure 2.1.1 as well as cooling by convection (Cundall
Johnston & Partners. 2004). Another productive way to introduce night air throughout
a building is by inducting or promoting cross ventilation. Night flushing offers the
potential to minimize or even avoid the use of mechanical cooling and improve the
internal conditions in naturally ventilated buildings. Accurate design of night flushing is
required in order to achieve maximum natural cooling while avoiding overcooling and
subsequent reheating or thermal discomfort the following day (Free Night Cooling
2009). “The performance of night flushing and the output of thermal mass cooling can
be estimated using thermal modeling and air flow analysis. These tests make it possible
to predict the likely nighttime air movement patterns through the building, and the
effects of varying window opening areas on each floor (Cundall Johnston & Partners.
2004).” Night flushing can be simply thought of as the thermal mass exchanging heat
and coolth depending on what the air and temperature of the building is.
17

Figure 2.1.1 – Night Flushing Ventilation Paths - 1. “Night flushing” removes heat from thermal mass
leaving “coolth” for the next day. 2. Stack cooling – hot air rises (up stairs, in “cooling chimneys” or in
roof vents) to be replaced by cooler night breezes that absorb heat from the thermal mass. 3. Thermal
mass loses heat to the cross ventilation or stack ventilation, known as “night flushing.” 4. Night-time
cooling breezes come from south and south east in summer, autumn and spring.

2.2 - The Ideal Climate Zone
Night flushing is most effective in climates with dry hot days that are followed by
cool nights. The climate needs to have low relative humidity and drier air to effectively
natural ventilate, otherwise moisture could be introduced into the building during the
following day, causing condensation. Natural ventilation is more successful in moderate
climates, with large diurnal temperature swings, than ones that have climates that are
either extremely hot or cold. Climates in which night flushing would be extremely
effective in are California, desert climates, and the high elevation areas of the southwest
United States. Climates that are hot during the day and cool at night can use natural
ventilation at night to expel the diurnal heat gain. These climates also offer a classic
example of the time lag effect of thermal mass (Thermal Mass 2007).The Building
Service Research Association in the UK have suggested that night time cooling should be
initiated if any or a combination of the following occur: peak indoor zone temperature
exceeds 23°C (73.4°F), average zone indoor temperature exceeds 22°C (71.6°F), and
18

average afternoon outdoor temperature is higher than 20°C (68°F) (Hardy 2009).They
also conclude that night time cooling should continue to be used if all of the following
criteria occur: The indoor zone temperature is higher than the outside air temperature
+2°C (4°F), the indoor zone temperature is higher than indoor heating set point, and the
outside air temperature is higher than 12°C (53.6°F) (Hardy 2009). The most important
factor of night flushing is the diurnal temperature swing, without it the night time air
and the thermal mass will not be able to work in unison.
Studies have shown that ventilation through night flushing can eliminate the
need for air conditioning in coastal-influenced California climate zones and can
significantly reduce total and peak demand air conditioning energy consumption
(NightBreeze Product and Test Information 2004). In today’s society, refrigerated air
conditioning has become the accepted way to cool a building, even if the local climate
can be used for natural ventilation. Even throughout California, the implementation of
passive design strategies can be as effective as mechanical cooling strategies in keeping
buildings thermally comfortable and cool. Passive strategies can offer a substantial first
cost savings while reducing mechanical system operating cost and overall building
energy consumption (NightBreeze 2009).
An initial step to successfully designing a passively cooled building is to
understand the local climate. Climate Consultant is a comprehensive tool for graphically
understanding weather data and is available free on-line (www.aud.ucla.edu/energy-
design-tools). Climate consultant displays climate data in a series of graphs and charts in
19

order to conduct an analysis of the climate zone. It uses EPW weather files that can be
obtained from the U.S. department of energy website, http://apps1.eere.energy.gov/
buildings/energyplus/cfm/weather_data.cfm. The types of climate data that are
graphically displayed are temperature, wind velocity, sky cover, percentage of sunshine,
the psychrometric chart, a timetable of bioclimatic needs, and sun charts (Milne 2007).
The psychrometric chart (Figure 2.2.1) shows the hours of the year a particular
climate is within the necessary temperature ranges for a particular heating or cooling
strategy. With this data it can then be determined what strategy best suits the particular
climate being studied. Climate Consultant will be used in this thesis for extensive climate
analysis of the location of the case study. The chart not only recommends which
Figure 2.2.1 - Psychrometric Chart for Climate Zone 12
20

building design strategies to use, but it also quantifies how effective each will be.
Weather data can be plotted on the psychrometric chart in many different ways in order
to reveal different types of climatic conditions. In Figure 2.2.2 every hour of the year is
plotted, the red dots indicate hours that the weather is above the comfort zone and
blue indicates the hours that are below the comfort zone. The chart also shows the
zones in which the hours of the year reach an acceptable climate level for different
design strategies. The Table of Effective Design Strategies shows that California climate
zone 12 is in the comfort range for 5.9% of the hours of the year. This example shows
that for California climate zone 12 night flushing is the best design strategy for hot
conditions for 15.1% of the hours of the year (Milne 2007). Climate Consultant’s
weather and climate analysis offer a strong starting point to understanding a specific
region. From all of the data gathered on solar positioning, rainfall, humidity, wind, and
temperature, a building can be designed to benefit from or design against these natural
conditions of a specific climate region. The EPW files that Climate Consultant analyzes
do not reflect the actual temperature swings that are experienced, but they still give
appropriate strategies for designing to specific climates conditions.

2.3 - Benefits of Night Flushing vs. Mechanical Cooling
Natural ventilation has become an increasingly effective method for reducing
energy use and energy cost per kWh. It provides an acceptable indoor environment by
maintaining a healthy and comfortable indoor environment. “In favorable climates and
21

buildings types, natural ventilation can be used as an alternative to air-conditioning
plants, saving 10%-30% of total energy consumption (Walker 2008).”Mechanical
ventilation, on the other hand, is an essential part of building design and operation in
order to deliver a more controlled and comfortable thermal environment and the best
possible indoor air quality, but it brings with it a significant energy load. To avoid this
energy load, natural ventilation strategies have been developed and applied to buildings
to minimize energy demand and to utilize the cooling potential of outdoor air
(Santamouris 2007).The heating, ventilation and cooling loads of typical commercial
office spaces can range between 30-50% of the total energy load of the building (Osburn
2009).For this reason, natural ventilation strategies like night flushing were developed
and applied to buildings to minimize energy consumption and to utilize the cooling
potential of outdoor air (Santamouris 2007). Night flushing can benefit a building in
several different ways:
• It saves energy and thus lowers utility bills.
• Providing outdoor air.
•It decreases the chance for mold and other ventilation-related claims.
•Reduces daytime mechanical air-conditioning load.
• Optimizes the performance of the thermal mass of the building.
Night flushing and ventilation can also have a very positive effect on internal
conditions during the day. The four main ways are (Santamouris 2007):
• Reducing peak air temperatures.
22

• Reducing air temperatures throughout the day and, in particular, during the morning
hours.
• Reducing slab temperatures.
• Creating a time lag between external and internal temperatures.
To achieve the benefits of night flushing on the indoor comfort, the performance
depends on three main parameters. The first parameter is the temperature and the flux
of the ambient air circulated in the building during the night. The second is the quality
of the heat transfer between the circulated air and the thermal mass. The third
parameter is the thermal heat capacity of the thermal mass (Santamouris 2007).These
three factors must work together in order for natural ventilation to be used primarily
over mechanical cooling. The fact that three separate parameters have to work in
unison makes it that much harder to consistently work.
The opposing figure to natural ventilation methods is mechanical cooling. The
intensive use of air conditioning is the result of many processes. A cultural reason is the
changes in comfort culture, consumer behavior and expectations. The building function
that directly affects whether a building uses air conditioning is the increase in the
building’s internal heat load. Lots of people probably feel that they would rather pay for
the convenience and the guarantee that an air conditioner can provide. They would set
their systems and not have to worry about it again. Despite the global desire for
mechanical cooling systems, these systems do have their faults. Mechanical cooling
leads to an increase in absolute energy consumption and the peak electricity load.
23

These systems are linked with environmental problems like ozone depletion and global
warming. They also have the ability to negatively affect indoor air quality; an example
would be the spread of Legionnaires disease (Santamouris 2007). When cooling a
building, there does not have to be an end all solution of mechanical or natural. The
best way to cool a building is to use both strategies together.

2.4 - Building Design Features that Enhance Night Flushing
The ways to maximize and improve the efficiency of night flushing are based on
passive cooling techniques, building design, and architectural features. One method of
enhancing night flushing is by altering the construction material and size of the thermal
wall or floor. Night flushing is more effective in buildings with high amounts of thermal
mass and when the thermal mass is exposed. Covering the thermal mass in any way
would hinder the effectiveness of the mass and its ability to store heat and coolth.
Raised access floors are increasingly common in buildings designed for night flushing
because of their ability to store heat in an underground cavity. The use of suspended
ceilings and any type of flooring finish insulates the thermal mass both from being
cooled by the night air and from the heat that is being generated during the day, both of
which is undesirable (Osburn 2009).
The size and density of the thermal mass are extremely important factors.
Masonry and concrete floors, walls, and ceilings that are used as thermal mass should
be a minimum of 4 inches thick (Stuart 2009). Once the thickness is greater than 4
24

inches, then the material plays a huge role in determining the size of the mass.
Table2.4.1 shows the different types of thermal mass materials as well as their thermal
properties. No matter what type of mass is selected, the most important variables for
determining how much heat and coolth the mass can store are its heat capacity and
density. Water has the highest volumetric heat capacity of all commonly used materials.
Adobe brick works as good thermal mass in the desert climates with high diurnal
temperature swings. Earth material’s heat storage capacity is dictated by its density,
moisture content, and temperature. Earth material can provide a fairly constant
moderating temperature that reduces heat flow between rooms. Rammed earth

Table 2.4.1 – Latent Thermal Storage Mass Materials
provides excellent thermal mass because of its high density and the high specific heat
capacity of the soil used in its construction (Charis 2002). Natural rocks and stones are
25

good forms of thermal mass because of their ability to hold temperature well (Rock
2001).The thermal conductivity of concrete depends on its composition and curing
technique. “Concretes with stones are more thermally conductive than concretes with
ash, perlite, fibers, and other insulating aggregates. Insulating concrete forms provide
the specific heat capacity and mass of concrete (Charis 2002).” The density of the
concrete determines how much area and mass the heat capacity can actually store.
Natural cooling can also be boosted when air flow is maximized. Natural
ventilation systems rely on pressure differences to move fresh air through buildings.
Pressure differences can be caused by wind or the buoyancy effect created by
temperature differences. The amount of ventilation will depend critically on the size
and placement of openings in the building (Walker 2008). The best way to maximize
natural air flow is through operable windows. Operable windows can have restricted
openness or seals so air cannot escape. Another alternative is to have openings at the
top and base of an atrium that introduces cooler air by drawing warm air up and out,
casement windows work very well for drawing in air flow (Energy Efficiency 2009).
Lowering a building’s internal heat gain can greatly increase the effectiveness of
night flushing. Most problems with night flushing involve the interior of the building
gaining too much heat from the sun, lighting, equipment, and human sensible and latent
heat. To support this effect, the solar shading should be lowered throughout the day to
minimize the heat impact of the sun. A building oriented toward the path of the sun and
wind might have a facade that uses balconies, windows, air intakes, and sunshades to
26

modulate solar heat gain. Natural lighting lowers internal heat gain, landscaping can
provide shade, and a building's color can determine how much solar heat is absorbed
(Malin 2009). Improving the thermal envelope is also a key feature that must not be
overlooked. The building envelope provides the thermal barrier between the indoor
and outdoor environment, and its characteristics and effectiveness play a direct role on
the building's energy consumption. Improving the thermal envelope will reduce the
amount of heat trying to enter the building during the day thus reducing the internal
heat impact.
All of these features that can enhance night flushing cannot work individually;
they all have to work together. By changing the internal and solar heat gain of a
building, how does this affect the building in the winter? Will it need more heating?
Every time one aspect of a building is altered it directly affects another feature of the
building or the buildings entire passive or active system. Critical features for night
flushing are the thermal mass, operable windows, solar gain, and internal heat gain.
There are many ways to enhance each of these features for night flushing; the key is
getting them to work as one.

2.5 - Thermal Mass
Thermal mass is a building material that can absorb, store, and later release heat
into and out of a space. Buildings constructed of high thermal mass materials have the
ability to store heat because of its density and inherent heat conductivity. These
27

materials absorb heat, coolth, and energy slowly and hold it for much longer periods of
time than do walls made of other materials. The heat absorption process is shown in
Figure 2.5.1.

Figure 2.5.1 – Thermal Slab Heat Absorption
The process of a thermal mass’ heat absorption delays and reduces heat transfer
through a building, leading to three important results:
• There are fewer spikes in the heating and cooling requirements, since the thermal
mass slows the response time and moderates indoor temperature fluctuations
(Concrete 2009).
• A massive building uses less energy than a similar low mass building due to the
reduced heat transfer.
• Thermal mass can shift energy demand to off-peak time periods when utility rates are
lower.
Since power plants are designed to provide power at peak loads, shifting the peak load
can reduce the number of power plants required (Concrete 2009).
28

Thermal mass materials like concrete, earth, and water can store an abundance
of heat. Because of this capacity to act as a heat source that warms its surroundings or a
heat sink which draws heat and coolth from their surroundings, materials with thermal
mass affect comfort both indoors and out.
Thermal mass has a certain time lag between the mass and the outside air as
shown in Figure 2.5.2. It saves energy in some climate conditions, but the effect is very
circumstantial. The most effective thermal storage materials are fairly good conductors
with a high heat capacity and thus are poor insulators with a low R-Value. “A thermal
mass like poured concrete insulates poorly with R-0.08 per inch, compared with R-3.70
for cellulose. But even in climates where insulation is the priority, buildings can use
thermal mass (Thermal Mass 2007).”In climates where significant cooling is needed,
thermal mass outside the insulation can also save costs by delaying the peak cooling
period until the night, when buildings are unoccupied and need less cooling, electricity
may be less expensive and cooling equipment operates more efficiently. Many uses of
thermal mass can reduce energy consumption and improve comfort. In buildings that
have no set occupied hours, it is often more efficient to minimize the interior mass so it
can absorb heat or coolth and get hot or cool rather quickly. Also, thermal mass can be
expensive and space-intensive, so architects and builders tend to use it where it serves
more than one function. It could be used as a structure or as a durable interior surface
like flooring (Thermal Mass 2007).”

29

Figure 2.5.2 – Storage Mass Time Lag
Thermal mass in terms of night flushing is for summer cooling. Thermal mass
combined with effective shading and ventilation strategies might eliminate the need for
mechanical cooling. However, large thermal mass can be disadvantageous in winter if
the building is not in constant use or has discontinuous heating. In this case, heating up
a large mass takes a long time. A thermal mass material’s heat storage capacity is
characterized by the mass and its specific heat capacity. The typical heat capacity of
building materials is 0.8 to 1.0 kJ/kgK. The ability of a thermal mass to absorb and
release heat is mostly determined by it conductivity. Materials with high conductivity
like metals insufficiently store heat, they heat up and cool down too quickly to work as
an effective thermal mass (Thermal Mass 2009).
This process is too slow in low conductivity materials. If a building is properly
insulated and airtight with few areas of infiltration, then heat losses can be minimized
and the building can be more effectively cooled by night time ventilation. Thermal mass
absorbs a large portion of solar and internal heat gains during the day. These gains can
30

be released from the building by flushing the thermal mass with cool night time air by
leaving windows open or by mechanical ventilation. Typically 2 – 5 air changes is the
goal in a ventilating a building, regardless if it is done with or without mechanical
ventilation. If fans are used, more air changes will require more electricity.

Figure 2.5.3 – Thermal Mass Heat Flow Peaks

Thermal mass has many influential factors and characteristics; it delays and
reduces peak loads as shown in Figure 2.5.3, it reduces total loads in many climates and
locations, and it works most effectively when mass is exposed on the inside surface.
These main factors all aim to reduce a buildings overall temperature and reduce or
31

eliminate the need for natural cooling. Figure 2.5.4 shows an example of what type of
effect night flushing with thermal mass can have on a building’s interior temperature
when mechanical cooling is not being used in a California climate. The results are
expected and prove that this method of passive cooling is valid.

Figure 2.5.4 – Night Flushing Reduced Interior Temperature

A material’s thermal resistance (R-Value) and thermal transmittance (U-Value)
do not take into account the effects of thermal mass. They do not describe the heat
transfer and heat capacity properties of materials or thermal mass. Heat capacity
(Btu/ft
2
·°F) can be defined as the amount of heat energy needed to raise the
temperature of a mass one degree Fahrenheit. The total heat capacity of a wall is
determined by the total heat capacity of the entire wall, the thermal mass as well as the
exterior finish and all other layers.
32

The amount of air that is actually needed to reduce the temperature of the mass
is a significant factor. Measures that are used to determine the reduction of the
thermal mass’ temperature are specific heat capacity and the weight/cubic foot of the
mass’ material. An example is determining how many cubic feet of air would have to
increase 1°F to drop the temperature of 1 cubic foot concrete by 1°F.
Specific Heat Capacity (Cp) of Concrete
- Cp = .22 BTU/lb
- Weigh of Concrete = 140 lb/cubit feet
- 30.8 BTU’s per 1 cubic ft. of concrete to raise 1°F

Specific Heat of Air
- Cp = 1.012 J/g.k
- .02 BTU’s per 1 cubic ft. of air to raise 1°F
- To drop the temperature of 1 cubic ft. of concrete by 1°F, 1540 cubic ft. of air
would have to increase by 1°F.

The thermal mass is by far the most important factor in night flushing. Without
it, then the building would just be cross ventilating at night. In order to achieve the most
effective night flushing, the thermal mass must be able to absorb enough coolth and
night in order to absorb heat for as long as possible throughout the day. The ideal
situation would be the thermal mass absorbing heat long enough through the day, so
mechanical cooling would not be needed. The most realistic material to achieve this for
a building is concrete. The type of concrete depends on the climate of the building. This
will dictate the density needed to achieve the longest possible heat storage capacity.
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2.6 - Disadvantages of Night Flushing
Even with all of the advantages to night flushing, there are several drawbacks.
An area of concern is opening and closing the operable windows at the appropriate
times. The onus is often on the owner or the occupants to operate the windows. In a
commercial building this responsibility would be put on the facilities manager. With
putting this function in the hands of the occupier the element of human error is now
factored in. A way that this is solved is by putting a motorized mechanism on the
windows that opens and closes on a timed schedule or a temperature differential
between interior and exterior temperatures. This eliminates the possibility that
someone forgets to open the windows at night and the building has no cooling for the
next day or that someone doesn’t close the windows in the morning and then the
building lets in direct hot air.
There are other concerns with security, air quality, and noise. One main concern
with flushing night time air one hundred percent naturally into a building overnight is
that opening windows during non-occupied hours can be a security liability. The
problem is that windows would have to be open during the night on the lower floors
where it is necessary for the air to be circulated into the building. This poses the
potential problem of theft, trespassing, and vandalism. “The open windows may also
make it more difficult to pressurize corridors and prevent smoke migration in case of
fire (Malin 2009).”One solution to this is to bring in the outside air through a dampered
ventilation duct. The duct is directly connected to the exterior skin and it has a louvered
34

grill that opens and closes on a timer or in correlation with a thermostat (NightBreeze
Product and Test Information 2004). Another drawback of night flushing with operable
windows is that it may introduce pollen, dirt, dust, toxins, and other outdoor allergens
into the interior of the building. A solution to this would be to use the dampered ducted
system with a MERV filter. This would essentially work like an air handler unit that
brings in outside air and filters it before it enters the unit and is then sent into the
supply duct to be circulated throughout the building, This is an effective strategy but
then the cooling system would no longer be a passive technique, it would be a forced air
mechanical system.
Other concerns with night flushing are its acoustical issues. Acoustics are an
issue both in bringing in noise from outside and in increased sound transmission from
openings provided for air flow (NightBreeze 2008). The noise concern is more of a
problem for residential buildings or buildings with late occupancy. If a building is being
occupied than exterior traffic noise and other outdoor sounds can be a distraction to
someone trying to sleep or work. In a commercial building that has little to no late night
occupancy then the acoustics become a non-issue.
The effectiveness of night flushing on still nights is another disadvantage. There
are nights when there may not be a sufficient amount of outdoor airflow to adequately
flush the building with cool air (NightBreeze Product and Test Information 2004). A
building could use window fans and whole house fans to provide increased airflow and
improve cooling, but this also requires windows to be opened (NightBreeze 2008). The
35

fans would help move the tranquil air as well as move the stale indoor air out. A
problem with this tactic is that it would require the windows to be open which brings
back the problems with open windows at night. It also no longer makes the system one
hundred percent natural ventilation. The power needed to operate the fan motors
would affect the electrical load, but compared to the energy load needed to run a
mechanical cooling system the load would be far less significant.
Temperature control is another concern for buildings with night flushing.
Occupants struggle with knowing when to open the windows at night and when to close
them in the morning. The occupants are in charge of knowing what the weather is going
to be and how to adjust their windows in accordance. This is very difficult to know and
somewhat unpredictable. If people don’t open and close the windows at the correct
hour, then their building might be uncomfortably hot the next day. When the building
uses motorized operable windows, there is still a question as to when to set the timer
for the windows to open. The way to make this problem less of an occupant control
issue is to use a thermostat that controls when to open and close windows in
accordance with the temperature swing. Another dilemma is how night flushing works
if it rains. Granted, it rarely rains in climates that would usually use night flushing, but if
it does then there is a problem. If the building has shading devices over the windows
they could assist in blocking rainfall from entering the building. The biggest issue with
using night flushing is its climate specificity. It can only be used in certain climates with
diurnal temperature swings like California. Night flushing would be extremely
36

ineffective in humid climates like Florida because night flushing cannot control relative
humidity. Humid climates experience much smaller diurnal temperature swings. And
night flushing in a sub tropic climate like Florida would introduce high levels of humidity
into the interior of a building during the night which could result in condensation
forming the following day. In order to use night flushing the air would need to be
dehumidified and then the air would be mechanically altered and that defeats the
purpose of night flushing.

2.7 - Hybrid Ventilation and Cooling Systems
It is valuable to understand the other types of natural ventilation strategies that are
currently being used that have similar intentions as night flushing. Unique systems that
are used that combine natural and mechanical systems are called hybrid ventilation and
cooling systems. They typically use outdoor air within their system to reduce energy
consumption and energy loss.
A hybrid ventilation system is a building system that combines natural and
mechanical ventilation and cooling for building comfort and indoor air quality
(Santamouris 2007). The International Energy Agency – Energy Conservation in
Buildings and Community Systems offer three hybrid ventilation systems: natural and
mechanical ventilation, fan-assisted natural ventilation, and stack and wind assisted
mechanical ventilation. Natural and mechanical hybrid ventilation is based on two fully
independent systems where the control strategy either switches between natural and
37

mechanical systems, or uses one for some tasks and the other for different tasks. It
covers systems with natural ventilation in intermediate seasons and mechanical
ventilation during midsummer or midwinter (Santamouris 2007). It also can use
mechanical ventilation as a backup to natural ventilation. If a building has used night
flushing and the building the next day is still too hot, the mechanical cooling will kick in.
Fan assisted natural ventilation is based on a natural ventilation system
combined with a supply or return fan. It covers natural ventilation systems that, during
periods of weak natural driving forces or periods of increased demands, can enhance
pressure differences by mechanical, low pressure, fan assistance (Santamouris 2007).
The most typical example of this is a whole house fan. A whole house fan is a fan that
pulls hot air out of a building through the ceiling and expels the hot air into an attic or
directly to the outdoors. When a building uses night flushing, the hot air needs to be
removed at night as the cool exterior air is entering the building. The fan helps to get
that air moving, instead of waiting for the heat to naturally rise.
Stack and wind assisted mechanical ventilation is based on a system that makes
optimal use of natural driving forces. It covers mechanical ventilation systems with very
small pressure losses, where natural driving forces can account for a considerable part
of the necessary pressure. This basically involves a typical mechanical cooling system
that supplies air to a space and allows stack ventilation to move the air throughout the
space. This reduces the energy needed to run the fan, sending air throughout the
building (Santamouris 2007).
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An outside air makeup air unit is a mechanical cooling system that uses outside
air and mixes it with air conditioning when the outdoor air is cooler than the interior
temperature. In the California climate, this would be sufficient. It supplies occupants
with mechanical cooling during the day and conserves energy at night by using outside
air to assist the air handler unit or the air conditioner.
NightBreeze is an integrated night ventilation cooling system with adaptive
controls for optimizing cooling comfort and energy savings. The system integrates
heating, ventilation cooling, air conditioning, and filtered outdoor air ventilation for
indoor air quality. When the indoor temperature is cooler than the outdoor
temperature in the summer months, the system will introduce outside air into a building
through a damper and ventilation ducts as shown in Figure 2.7.1. In the winter, it heats
the house using heat from the water heater or furnace (NightBreeze 2008).

Figure 2.7.1 – NightBreeze Ventilation Duct
39

The main features of NightBreeze are (NightBreeze Product and Test Information
2004):
• An automatic damper that allows a building to be ventilated and cooled using filtered
outside air, without the necessity to open windows.
• A control system that anticipates hot weather and automatically ventilates with cool
night air to provide optimal comfort while minimizing air conditioner energy use.
• A quiet, efficient, variable speed blower that provides just the amount of airflow
needed to meet heating and cooling needs.
• A furnace that obtains its heat from your water heater instead of from direct gas
combustion, thereby improving building safety.
• A thermostat that is easy to use and provides built-in help.
NightBreeze provides ventilation cooling automatically, eliminating the necessity
of operable windows. NightBreeze uses the heating/air conditioning system fan to bring
in filtered outside air and flush out warm, stale indoor air. The system also allows you to
select the lowest temperature you want the house to reach overnight. As the weather
becomes milder, the system automatically decreases the amount of ventilation to
prevent the house from being over-cooled (NightBreeze Product and Test Information
2004).
Heat recovery ventilator (HRV) brings in pre-heated or pre-cooled fresh air from
the outside. A residential HRV moves stale air out of a building and brings fresh air in
using separate blowers.“The heat-exchange core transfers heat to fresh air without
40

mixing the airstreams. The damper automatically stops cold air for defrosting (Klenck
2000). An HRV is designed to be energy efficient and exchange the air to bring in fresh
filtered and clean air at a rate the occupant chooses. It also exhausts stale air,
pollutants, and moisture, while recovering up to 85% of the heating or cooling energy
(Heat Recovery Ventilators 2009).

2.8 - Previous Night Flushing Studies
There have been a multitude of previous studies in regards to night flushing,
many of which have studied a different aspect of the passive cooling strategy. There
have been three particular research studies that take on different approaches to
studying the potential and effectiveness of night flushing. Students from Purdue
University developed a simulation tool to evaluate a proposed night ventilation control
algorithm for packaged air-conditioners. Professor Pablo La Roche of California State
Polytechnic University – Pomona and Professor Murray Milne of UCLA designed an
intelligent control system that manages air flow according to cooling needs in a building
and resources in the environment to increase the application of night flushing and
daytime comfort ventilation. A student at Aalborg University in Denmark did a PHD
thesis on developing a method for quantifying the climatic cooling potential (CCP) based
on degree-hours of the difference between building and external air temperature to
discover the potential for night time building ventilation.
41

Night Ventilation with Building Thermal Mass by Jim Braun, Kevin Mercer, and
Tom Lawrence of Purdue University examined ventilating with cool air throughout the
night and early morning hours to reduce the temperature of the building mass as an
alternative to leaving HVAC equipment off during unoccupied hours. They were looking
to take advantage of the thermal storage capabilities of the building structure to
transfer a significant portion of a building’s on-peak cooling requirements to off-peak
periods, reducing both energy and demand costs (Braun 2003).The goal of the project
was to develop a simulation tool to evaluate a proposed night ventilation control
algorithm for packaged air-conditioners with economizers, such as rooftop units. The
hope was that the algorithm would help them develop, implement, and demonstrate a
control strategy for using night time ventilation and building mass to reduce cooling
requirements and peak cooling demand while ensuring adequate thermal comfort. So
first they developed their algorithm and simulation tool, and then they evaluated the
control algorithm with field tests. Their next step was comparing the field monitoring
data and the simulation data and improving the algorithm based on the comparisons.
The final step was summarizing the results and present recommendations regarding the
overall potential for cost savings using night ventilation with building mass in California
applications.
The algorithm was tested in simulations and a retail building located in southern
California. The simulated building types included small office buildings, sit-down
restaurants, retail stores, and schools spaces such as the classrooms, the auditorium,
42

the gymnasium, and the library as shown in Figure 2.8.1 (Braun 2003).The greatest
savings were expected for buildings in coastal climates. Significant savings were also
predicted for hot inland climates. Depending upon the building and HVAC system, the
estimated daily savings in costs for buildings associated with nighttime ventilation were

Figure 2.8.1 - Mechanical Night Ventilation Cost Savings in California for Different Buildings

between about 10 and 50% when compared to conventional night setup control. The
electrical energy savings were between zero and about 8%. The electrical demand cost
savings associated with night ventilation varied between zero and about 28%, whereas
the total electrical cost savings ranged from zero to about 17% (Braun 2003).
The study’s conclusions were that the night ventilation pre-cooling strategy can
be implemented using the same sensors and control hardware employed within an
43

economizer controller. Therefore, it should be cost effective to integrate night
ventilation control with economizers for packaged equipment used in small commercial
buildings. Even greater savings should be possible for packaged units that use variable
speed fan control. If night precooling is being considered for a new design, a return air
damper should be specified and controlled so that it closes during night ventilation
precooling. Applying night ventilation precooling to existing construction will probably
require retrofitting controller hardware (Braun 2003). The difference between the
Purdue study and this thesis is that this thesis will show how long a building can remain
thermally comfortable without the use of air conditioning based solely on the use of
pre-cooling the building structure.
Effects of Thermal Parameters on the Performance of an Intelligent Controller for
Ventilation by Professor Pablo La Roche and Professor Murray Milne studied how to
increase the application of nocturnal flushing and daytime comfort ventilation. They
designed an intelligent control system that manages air flow according to cooling needs
in a building and resources in the environment. This system is a microcomputer-
controlled thermostat with both indoor and outdoor temperature sensors that can
control a whole-house fan, in addition to the furnace and air conditioner. The rules for
assorted control strategies were programmed and tested using two slab floor test
models as shown in Figure 2.8.2. Their test proved to be successful in reducing both the
maximum temperature and the number of overheated hours in the test model,
compared to the control model. This project demonstrated the feasibility of a new kind
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of intelligent ventilation controller that can minimize cooling energy costs for California
homeowners (La Roche). It showed that this controller always reduced the peak indoor
temperatures and the number of overheated hours.
This controller system knows how much night-time air should be brought in to
cool the building's interior mass so that it can be comfortable throughout the next day.
The controller is similar to a conventional programmable thermostat, but with the
addition of an outdoor temperature sensor and a microprocessor to hold the expanded
control logic (La Roche). The house needs to have a whole-house exhaust fan and a
strategy for operating windows or air inlets, and as much internal mass as possible. The

Figure 2.8.2 – LaRoche and Milne Test Cells
building performance simulation study shows that a smart thermostat and a whole
house fan would provide significant savings to Southern Californian ratepayers. When
comfort low is lowered to 65° F, there is an enhancement in the performance of the
system because the hot hours and the maximum temperature are reduced. The
45

reduction of comfort low, increasing thermal amplitude, is probably the single most
important factor to be considered when using natural ventilation, because it increases
the capacity of the building to flush the heat stored inside, to store coolth (La Roche). To
be effective, night temperatures should be below 21° C and close to 18° C. These are
reached at night during the summer in many parts of southern California, especially in
the inland and desert regions. An advantage of an intelligent thermostat controller that
measures outdoor air temperatures, compared to a system that measures only the
indoor air temperature, or a system with a fixed timer, is that the intelligent controller
increases the air change rate whenever it is needed and when resources for cooling are
available, rather than at times when it unintentionally heats the building. With an
intelligent thermostat controller it is possible to maximize the performance of the mass
in a building, to achieve better cooling results than in a building with more thermal mass
that isn’t provided with an intelligent controller for natural ventilation cooling (La
Roche). The idea behind the intelligent thermostat controller is very effective and it
incorporates the same goal as this thesis, to maximize thermal mass to achieve natural
cooling.
Cooling of the Building Structure by Night-Time Ventilation by Nikolai Artmann is
a PHD thesis that studies the potential for passive cooling of buildings by night-time
ventilation was evaluated by analyzing climatic data, without considering any building-
specific parameters. He developed a method for quantifying the climatic cooling
potential (CCP) based on degree hours of difference between building and external air
46

temperature. The study applied this method to climatic data over 259 stations, and it
showed very high night cooling potential all over Northern Europe and in Central,
Eastern, and some regions of Southern Europe. In order to assess the impact of different
parameters, such as slab thickness, material properties and the surface heat transfer,
the dynamic heat storage capacity of building elements was quantified based on an
analytical solution of one-dimensional heat conduction in a slab with convective
boundary condition (Artmann). The potential of increasing thermal mass by using phase
change materials was also estimated. The results show a significant impact of the heat
transfer coefficient on heat storage capacity, especially for thick, thermally heavy
elements. For thin, light elements a significant increase in heat capacity due to the use
of phase change materials was found to be possible (Artmann).
In order to identify the most important parameters affecting night ventilation
performance, a typical office room was modeled using a building energy simulation
program HELIOS, and the effect of different parameters such as building construction,
heat gains, air change rates, heat transfer coefficients and climatic conditions on the
number of overheating degree hours was assessed. Besides climatic conditions, the air
flow rate during night-time ventilation was found to have the largest effect. However,
thermal mass and internal heat gains also have a significant impact on the achievable
level of thermal comfort. A significant sensitivity to the surface heat transfer was found
for total heat transfer coefficients.
47

The study’s results lead to the design of a practicable method for the estimation
of the potential for cooling by night-time ventilation during an early stage of design. In
order to assure thermal comfort two criteria need to be satisfied. First, the thermal
capacity of the building needs to be sufficient to accumulate the daily heat gains within
an acceptable temperature variation. The second is that the climatic cooling potential
and the effective air flow rate need to be sufficient to discharge the stored heat during
the night. The estimation of the required amount of thermal mass in the building is
based on the dynamic heat storage capacity. The air flow rate needed to discharge the
stored heat at a certain climatic cooling potential is assessed based on the temperature
effectiveness of the ventilation (Artmann). This study helped to confirm what aspects of
the climate and what building parameters play the largest role in trying to successfully
night flush a building. The type of thermal mass, air flow rate, and thermal mass have
the largest affect on night flushing and will be further studied in this thesis.

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Chapter 3: Case Studies

Three buildings were investigated as the possible case studies for this thesis; the
Lakeview Terrace Library, the California Science Center, and the Santa Clarita Transit
Facility. These three building were chosen because of their use of natural ventilation,
their construction, and their location. The Lakeview Terrace library is promoted as a
building that utilizes night flushing, making it a perfect candidate for a cased study. The
California Science Center has large amounts of exposed concrete and was looking for
someone to potentially do a night flushing study to reduce the building’s energy
consumption while utilizing the thermal mass. The Santa Clarita Transit Facility utilizes
an outside air economizer to draw in outside air and has an interesting sub-floor
concrete plenum that would make it an interesting night flushing study. The buildings
were thoroughly researched using journals, magazine articles, numerous on-site visits,
and meetings with the architects, mechanical engineers, and building staffs.

3.1 - Lakeview Terrace Branch Library
The Lakeview Terrace Library (Figure 3.1.1), located at 12202 Osborne Street
Lakeview Terrace, California, is a 10,700 square foot LEED Platinum building designed by
Fields Devereaux Architects & Engineers and GreenWorks Studio. The building program
includes the library, a community room, an environmental display gallery, and an
exterior courtyard. The building’s plan responds to the community’s desire for a library
that reflects the rancho tradition of the region, with interior spaces organized around an
49

open central courtyard as show in Figure 3.1.2. The open main reading room runs east
to west and gives views to the park to the south. The orientation of the building and its
architectural forms shield the interior spaces from direct sunlight, controlling heat gain
and preventing glare while maximizing daylight and views. The library is considered a
model of environmentally sustainable design and is a civic landmark (AIA 2004). It has
won several different awards for sustainable excellence: Runner up for the
Environmental Design &Construction Magazine Excellence in Design Awards in 2004, the

Figure 3.1.1 – Lakeview Terrace Library Figure 3.1.2 – Lakeview Terrace Floor Plan

Savings by Design Energy Efficiency Award, and the AIA Top Ten Green Projects in 2004
Award.
The library's energy performance was predicted, using an EnerygPro simulation,
to exceed California standards by over 40% and is 50% better than the ASHRAE 90.1-
1999 baseline (AIA 2004).Disappointingly, the current building performance does not
surpass these standards. The building shell is high thermal mass concrete masonry units
that is exposed on the interior and has exterior insulation. The local climate includes a
significant diurnal temperature difference, which combined with the exposed CMU walls

50

(Figure 3.1.3), is ideal for night flushing. Approximately 80% of the building is naturally
ventilated with mechanically interlocked windows (Figure 3.1.3) controlled by the
building's energy management system (AIA 2004). The window location and interior
volume shape were designed to maximize ventilation. This is extremely evident in the
large open reading room (Figure 3.1.4) where cool night air is brought in through the
operable windows on the south side and the hot air is naturally ventilated across the
ceiling and removed through the north side windows. The building also uses a passive

Figure 3.1.3 – Operable Windows & CMU Thermal Mass Figue 3.1.4 – Main Reading Room

cooling tower which takes the exterior wind and brings it through a wet pad that cools
the air and ventilates through the entry, the environmental display room, and the public
support spaces at the front of the building. Overflow air from the tower is directed
through the windows to cool the interior courtyard (AIA 2004).
A building-integrated photovoltaic system shades the entry, roofs the
community room, and provides 15% of the building's energy. The orientation of the
array maximizes production during peak cooling-load periods and contributes to ISO
Grid energy security (AIA 2004). The building is well insulated and roofed with Energy
51

Star compliant high emissivity roofing. The building is designed not to exceed 79
degrees Fahrenheit by using night flushing according to energy models using TMY2
weather data (AIA 2004). Digital controls direct sequences of operations that anticipate
cooling need based on trailing weather data to inform operations such as night venting
and window and relief vent operations as well as typical HVAC functions. HVAC systems
with variable-speed drives and pumps use non-HCFC refrigerants, and the building’s
temperature and humidity are controlled within ASHRAE 55 standards (AIA 2004).
Although the buildings EMS controls are highly automated, library staff is provided with
manual override capability and direct feedback from electronic monitoring of interior
thermal comfort. They can initiate the HVAC system if needed, or they can control the
windows operable motor system.
The design of the library provides nearly 100% shading of glazing during
operating hours. Glare control daylighting was an aspect of the building’s design. During
a typical day, all public areas and bookstacks (93% of the building) achieve target
lighting levels and appropriate brightness ratios without artificial light (AIA 2004). The
design of the window glazing protects the library from direct sun to reduce heat gain
and glare while maximizing daylight and views. The building’s windows use a type of
glazing with a low solar heat gain coefficient (SHGC) to help reduce the internal heat
buildup. Skylights provide daylight to bookstacks and offices. Photocells control lighting
circuits in all of the zones. The library also uses light shelves, overhangs, recesses, fins,
and louvers to harness the sunlight for superior interior light quality. A non-
52

architectural feature the building uses for shading is trees. Currently (2010) the trees on
the south side of library are five years old and only provide a limited amount of shading
due to the angle of the sun (Figure 3.1.5). In another five years the tress should be large
enough to adequately shade the windows all day and reduce the internal heat gain of
the library.

Figure 3.1.5 – Natural Shading from 2003 to 2009

The Lakeview Terrace Library is a building designed and awarded for its
environmentally sustainable passive cooling design. The building was designed to use
night flushing and thermal mass to naturally cool the building and extensively reduce
the energy needed for air conditioning. After an onsite investigation of the building and
conversations with Fields Devereaux Architects & Engineers, GreenWorks, the Director
of Building Operations, the Project Manager, and the staff, it has been determined that
the night flushing system and the passive cooling tower are both inoperable. The
motors for the operable windows (Figure 3.1.6) which are set to the EMS controls have
malfunctioned and there have been complications with getting
53

Figure 3.1.6 – Operable Window Motor

them to operate correctly. The passive cooling tower has never functioned as designed.
The tower was not receiving the adequate airflow to be effective and the spraying
mechanism to cool the incoming air has broken and not been fixed. What has been
brought to attention by Greenworks is that the library’s night flushing and cooling tower
were designed based on estimations, not by the use of a simulation tool. So, the library
has never actually been simulated for night flushing, and there is no documentation of
how it was designed or how it should perform. When the building’s construction was
complete, it turns out that the night flushing and cooling tower were both designed
incorrectly and were ineffective. The wind flow in cubic feet per minute was not high
enough to allow the systems to operate correctly. The library is currently working with
their consultant company to fix both issues but have been struggling to solve the
dilemmas. Currently the library is using their mechanical air conditioning system to cool
the building, and none of the passive cooling strategies in which this LEED Platinum
building was designed to use are currently functioning.
54

This research paper will explore why the night flushing is not working and it will
help determine how the building could be performing if the night flushing was properly
installed and functioning. Based on simulations of night flushing, conclusions can be
drawn on the effect of night flushing on energy conservation. A key element is the
passive cooling tower. The passive cooling tower is a 30’ natural draft evaporative
cooling tower that takes advantage of the reverse heat stacking effect by using a direct
evaporative spray cooling media (Figure 3.1.7). The tower actually acts as an inverted
chimney, instead of hot air rising and exiting, cool air is drawn into and down through
the stack. The tower takes advantage of the seasonal Sylmar, California winds and
thermal stratification for cooling with natural ventilation. The tower was expected to
deliver approximately 15,000 CFM of evaporative cooled air for the display room,
learning center within the tower, the adjacent lobby, the main reading room, and the
public restrooms. The air is then exhausted out through the operable windows into the
exterior courtyard. The cooling towers architectural components are the tower’s
maintenance platform, windows, grilles, baffles, and the shutters. The mechanical
components are the evaporative spray cooling media and its frame, the piping, the
pumps, the reservoir, valves, and controls.
The factors that were taken into account when designing the tower are the
tower’s height, the size and position of the evaporative media, the plan size of the
tower, the location of the tower in relation to the spaces served, and the size of the
tower’s outlet. The tower works by dropping the cooler air, after it has been sprayed by
55

Figure 3.1.7 - Cooling Tower Detail Figure 3.1.8 – Cooling Tower Air Flow Diagram

The factors that were taken into account when designing the tower are the tower’s
height, the size and position of the evaporative media, the plan size of the tower, the
location of the tower in relation to the spaces served, and the size of the tower’s outlet.
The tower works by dropping the cooler air, after it has been sprayed by the evaporative
media, down the tower into the lobby where it displaces the warm air causing it to rise
and ventilate out the window (Figure 3.1.8). The operable windows in the lobby are
placed at 6 feet so any hot air stratification happens above the occupants. The tower
56

operates when the indoor temperature is above 72° F, then the shutters and operable
windows open, and when the interior temperature rises above 76° F the evaporative
cooler circulation pump activates. The design for the cooling tower was done by the
Environmental Research Lab at the University of Arizona. The methodology behind the
tower is the ideal gas law, a modified version of Bernoulli’s principle of increased
velocity at lower pressure and the First Law of Thermodynamics. The equation for the
tower’s airflow velocity in the presence of wind is (Greenworks Studio):
𝑣𝑣 𝑡𝑡 = 𝑣𝑣 𝑤𝑤 �
1
∑ 𝐾𝐾 � 𝛥𝛥𝛥𝛥 𝑤𝑤𝑤𝑤 + �
𝛥𝛥 𝑓𝑓 𝜂𝜂 𝛥𝛥𝑡𝑡 𝑤𝑤 𝑇𝑇 𝑎𝑎 � � �
2 𝑔𝑔𝑔𝑔 𝑣𝑣 2
𝑤𝑤 � − 𝛥𝛥𝛥𝛥 𝑤𝑤𝑤𝑤 � �
where,
𝑣𝑣 𝑡𝑡 = Air velocity of at the bottom of the tower
𝑣𝑣 𝑤𝑤 = Air velocity of wind
𝑔𝑔 = Acceleration due to gravity
𝑔𝑔 = Bottom of pad height above tower outlet
∑ 𝐾𝐾 = Sum of pressure loss coefficients
𝛥𝛥 𝑓𝑓 = Density correction factor = .93
𝜂𝜂 = Pad effectiveness
𝛥𝛥𝛥𝛥 𝑤𝑤𝑤𝑤 = Difference between wind pressure coefficients at the tower inlet and outlet
𝑇𝑇 𝑎𝑎 = Atmospheric temperature
𝑡𝑡 𝑤𝑤 = Wet bulb temperature

The library has been awarded LEED Platinum status by the USGBC for LEED
Version 2 in 2005, and as a part of its rating, it achieved ten of the eleven prerequisites
and credits that pertain to natural ventilation. It met the prerequisites Minimum Energy
Performance and CFC Reduction in HVAC & R Equipment, which is now called
Fundamental Refrigerant Management for the Energy & Atmosphere category. For EA
credits it achieved 2 points for Optimizing Energy Performance and 1 point for Ozone
57

Protection which is now Enhanced Refrigerant Management. For the Indoor
Environmental Quality section, the library met the prerequisites of Minimum Indoor Air
Quality Performance. It achieved credits for Carbon Dioxide Monitoring which is now
Outdoor Air Delivery Monitoring, Increase Ventilation Effectiveness, Thermal Comfort:
Compliance with ASHRAE 55-1992, and Daylight and View for 75 and 90% of spaces. The
last LEED credit the library achieved in terms of natural ventilation was an Innovation &
Design Process point for Community Benefit. The point was based on the demonstration
of the passive cooling tower (Figure 3.1.9) and its attempt to use the building’s green
feature as an education tool as part of a comprehensive educational program. In order
to achieve this point, the library had to achieve two of three measures of educational
innovation. One measure was a comprehensive signage program built into the building’s

Figure 3.1.9 –Cooling Tower Interior Figure 3.1.10 –Signage for LEED Building Innovation
spaces to educate the occupants and visitors of the benefits of green building design
(Figure 3.1.10). The second measure was the development of a guideline report on “An
Integrated Approach Toward Implementing a Cooling Tower” to be used by the USGBC
for sharing with other projects. Reaching these LEED achievements shows the libraries
58

initial design intent to utilize natural ventilation for the better of the building and its
occupants.
The Lakeview Terrace Library will be the case study of this investigation. The
building’s design and natural ventilation inconsistencies between perceived and real
behavior make it the most intriguing case to further study. Night flushing will be
simulated in the building to see if and how effective it can be.

3.2 - The California Science Center Phase II
The California Science Center Phase II is a 190,000 square foot addition to the
existing Science Center that was originally remodeled in 1998. Phase II is scheduled to
be completed in 2011. Phase II two of the Science Center consists of World of Ecology
exhibit that is organized as a series of complex ecological environments. It has a 20,000
square foot rainforest exhibit, a 2,500 square foot desert zone exhibit, and an 180,000
gallon kelp forest. The addition also includes two administration floors that are the
third and fourth floor and an upgraded infrastructure for the entire museum. The idea
behind the design of Phase II is to bring an ecological approach to architecture. The
design concept is to have a green building using sustainable materials, natural systems,
and advanced technologies while conserving natural resources and energy
simultaneously (L’Italien 2009). The addition was also designed around the existing
trees, which in turn provide great shading for the buildings large glass curtain walls as
59

shown in Figure 3.2.1. This is a tremendous advantage because it helps to lower the
buildings internal heat gain.

Figure 3.2.1 – California Science Center Phase II Glass Curtain Wall

The study of the Science Center is on the indoor climate of the third and fourth
floor administration levels. The Phase II design did not incorporate night flushing into
their design even though administration floors have exposed thermal mass (Figure
3.2.2). The building right now is cooled fully by mechanical systems. The mechanical
setup consists of two chillers in the central plant, one of which runs on an adaptive
frequency drive. These chillers chill the water through the morning. At 1:00 pm, the

Figure 3.2.2 - Exposed Thermal Mass Ceiling Slab Figure 3.2.3 – Ice Tank Chillers
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two back up chillers kick in, they supply chilled water via two underground tanks that
store ice (Figure 3.2.3). At night during off hours when energy is cheaper the building
makes ice in two large underground storage tanks, then during peak hours they use the
ice to cool the building, reducing the need for utility companies to add capacity,
reducing the load at the period of greatest demand. The tanks are filled with white
plastic cubes filled with water and a cooling glycol mixture is passed through the tanks
to freeze them at night then during the day to cool the glycol. The glycol is a closed loop
running through the chillers and the buildings heat exchanger. All of the chillers send
the chilled water to the air handler units, there are two air handler units for the
administration building both located on the roof (Figure 3.2.4). Both have air side
economizers that can draw in 100% outside air at night when the temperature of the

Figure 3.2.4– CSC Rooftop Air Handler Unit Figure 3.2.5 – CSC Underfloor Air Supply

outside air is cooler than the temperature of the re-circulated conditioned air. Also
located on the roof are two cooling towers that are receiving the chilled and condenser
water from the pumps on the chillers. Each chiller is equipped with one condenser
pump and one chilled water pump that are both on variable frequency drives. The air
61

handler then supplies the cool air through a ducted under floor system through vents in
the floor (Figure 3.2.5). The supply and return fans are also on variable frequency
drives.
Phase II of the Science Center is complex and cooling is mechanically driven but
it has great potential for energy conservation through the use of night flushing and
passive cooling. A night flushing analysis of this building could determine how much
natural ventilation can be used during the night time to cool down the floor slab to save
energy and help to have the daytime room temperature be lower than the current
temperature at the peak cooling time. If night flushing is used, the optimal run time of
the fans will need to be determined to achieve maximum natural cooling. It will take
into account the start time, end time, and the amount of CFM the fans will need to blow
for optimal nigh flushing. Tests on the CSC could evaluate if the pre-cooling period, the
time necessary to bring the space to the desired indoor temperature, by the chillers may
be minimized or even eliminated by using night flushing. From determining this
information, the next step would be to quantify the energy savings the building would
have by using night flushing. Since the building has no operable windows the cool night
time air would be brought in mechanically through the air side economizer and it would
be funneled into the occupied spaces using the VFD fans. The other option would be to
make the windows operable. A large issue with the building is the west wall shown in
Figure 3.2.6. The wall is an uninsulated concrete wall that seems to be having increased
temperature swings throughout the day even with the air conditioning running. The
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mechanical engineering company for the building, Guttman and Blaevoet, believe that
the wall is performing as a mass wall. It is acting as a solar thermal collector. This
aspect of the building would need to be investigated to determine how the wall is
affecting the indoor climate and what to do with it.

Figure 3.2.6 – West Wall Concrete Thermal Mass

The California Science Center’s building engineers have provided valuable
information for a study. They information made available are the control diagrams for
the HVAC systems, the buildings sequence of operations, as well as the trend logs from
the EMS system showing data for indoor temperature for months. EHDD, the architects
for the building have also provided the building plans, sections, elevations, mechanical
plans, mechanical schedules, and a Revit 3D building model.
The California Science Center could have been a very interesting study for a
thesis, but its scope seems to be too large for the time allotted. Guttman and Blaevoet
have many areas that they would like studied but do not seem to have the backing of
the building engineers. The engineers were a bit reluctant to provide access to all of the
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areas of the building in which access would be regularly needed. This case study would
be a good project for future consideration, but for this study it was not the best choice.

3.3 - Santa Clarita Transit Maintenance Facility
The Santa Clarita Transit Maintenance Facility (Figure 3.3.1), located in Santa
Clarita, California, is a 25,000 square foot LEED Gold building designed by the
architecture firm HOK. It is one of the first LEED certified straw bale buildings in the
world. One of the most intriguing aspects of the building’s environmentally friendly
design is the straw bale construction of the building’s walls shown in Figure 3.3.2. Straw
bale as a wall component is durable, low-cost, nontoxic, highly insulating, pest-resistant,
and is especially practical in hot arid climates. Straw bale provides twice as high
insulation value as standard insulation materials and requires no wood or metal studs,
gypsum board, or paint. The result of building with straw bale is an energy-efficient
building that promotes a healthy indoor environment (HOK 2007).

Figure 3.3.1 – Transit Maintenance Facility Entrance Figure 3.3.2 – TMF Wall Section
64

The HVAC system is an efficient water-source heat pump. Chilled water is
generated by an on-site cooling tower. Under-floor air delivery (Figure 3.3.3) eliminates
the need for overhead ducts, leaving the ceiling unobstructed for better daylight
reflection. The mechanical system uses highly efficient MERV-13 air filters to remove
particles from the outside air before it is circulated into the air. The raised-floor system
uses concrete-filled metal pans, which are left exposed to eliminate the need for carpet
or other floor coverings in most spaces. The concrete filled raised floor panels set above
the concrete slab by about 14 inches. The under floor air delivery system delivers

Figure 3.3.3 – Raised Floor System

conditioned air through the diffusers mounted in the floor tiles. The air for the
occupants is cleaner because it does not mix with contaminated air near the ceiling, and
it does not warm up by passing through the hot zone near the ceiling before it reaches
the working plane. During the night the HVAC system uses an air-side economizer and
on most nights pulls in 100% outside air. The 100% outside air combined with the
concrete subfloor plenum act as a forced air night time flushing system. The desert
climate, with large diurnal temperature swings, is ideal for cooling by nighttime
65

ventilation. Cool night air is brought into the administration building where it chills the
interior surfaces' thermal mass, preconditioning the space for the following day (HOK
2007).
The building’s orientation and its U-shaped floor plan allow for optimal use of
daylighting features, such as skylights and clerestory windows, while dual-pane glass
with compressed argon gas selectively blocks heat. The building incorporates a well-
insulated roof combined with the thick straw-bale walls to create a super-insulated
envelope that moderates temperature fluctuations and protects the indoor
environment from the hot, dry daytime conditions. Deep roof overhangs shade the
glazing while protecting the perimeter of the straw bale walls from direct water
infiltration. The roof overhang extends eight feet beyond the face of the windows
reducing glare and heat buildup. The daylighting strategy reduces reliance on electric
lighting and the associated heat loads. Skylights over the interior corridors and lobby
limit the amount of electric light required in those areas (HOK 2007).
The facility’s night ventilation is not the same as night flushing. The system uses
an air-side economizer to draw in 100% outside air during the cool nights and brings it
into the building through dampered ventilated ducts. The air is filtered and then mixed
with the air conditioning. The raised concrete floor panels and the space created
provide a sufficient thermal mass, but it was not designed for cooling the building. The
thermal mass absorbs some of the air conditioned coolth but it does not really have to
absorb heat since the air conditioning runs throughout the day. The straw bale walls are
66

very strong insulators but have a weak thermal capacity. While the facility does not
currently use night flushing it has many features necessary for night flushing. It has
thermal mass concrete floor slabs above a sub-floor plenum. The straw bale walls are
great insulators so the heat from the exterior cannot quickly penetrate the building and
the coolth from inside cannot easily escape. Santa Clarita has a diurnal temperature
swing. There are plenty of windows that if made operable would allow for air to be
brought in at night. The 100% outside air that the economizer brings in can be used as
an alternative to operable windows. The building also has overhangs that shade the
windows and help reduce direct solar heat gain. This building is a great case study for
simulating night flushing in a building that does not currently use it. A lot of the
components are in place. A simulation could be done to determine what the results of
night flushing are and then tests would be conducted to show how to improve it to
make the indoor temperature ideal by maximizing the night flushing’s efficiency.
The Transit Facility will not be further investigated for night flushing due to the
climate of the Santa Clarita area – the city has extremely high summer temperatures.
Charles Smith of HOK and Andy Downs, the building engineer, have both said that the
temperatures are too high during the day and not cool enough at night for night flushing
The project might have been worthwhile to study if the EMS system had been storing
the internal HVAC data, but the system did not have the capabilities. The building is
very interesting but for this study it will not be taken any further than the initial
investigation.
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Chapter 4: Methodology

The Lakeview Terrace Library’s initial intentions to incorporate night flushing into
the building’s design may have been ineffective, but the library still has the potential to
implement this strategy. The library is in a prime climatic location with diurnal
temperature swings, and it already has exposed concrete thermal mass and operable
windows. The goal of this study is to investigate the Lakeview Terrace Library and what
type of effect night flushing can have on the building’s overall energy and thermal
comfort performances. In order to prove night flushing’s efficiency in the library, the
building will be simulated in the program Integrated Environmental Solutions – Virtual
Environment Pro. The results will be compared to energy consumption and interior
temperature data from the library’s initial design phase and data from the current
building performance. This will accurately set up a comparison of how much energy the
building was designed to consume versus how much energy the building is actually
consuming and how much energy the building could be conserving.
The data that will be important and necessary to collect from the simulation for
analysis are the factors needed for night flushing as well as the results of this natural
ventilation technique. One of the most important pieces of data desired from the
simulation is the library’s total energy consumption and carbon footprint. The basis of
the study is on lowering the total energy consumption. Another piece of data that will
be extremely valuable is the airflow movement analysis. This will show the movement of
the naturally ventilated air as it moves through the library and help determine if it is
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moving effectively for night flushing. The simulation can also provide the temperature
trends of zones as well as what times of day the temperature peaks. The simulation can
also provide HVAC performance data, so the energy simulation can include the energy
needed if fans are required to increase airflow. Other important data needed is the
effectiveness and overall heat capacity of the thermal mass, its time lag, and the
amount of time the concrete can absorb heat from the air. Running a simulation of the
library will provide all of the valuable data needed for testing the effectiveness of night
flushing.
The first step that will be taken in order to fulfill this study’s intentions will be to
collect the library’s design information. This includes all construction documents,
mechanical schedules, HVAC system and design parameters, and energy simulations.
Second, the current building performance data needs to be obtained. This includes the
energy consumption bills, the natural gas consumption bills, the energy management
system data (EMS), the Sylmar weather data, and installing HOBO devices for collecting
indoor climate data. Third, the building will be modeled in Revit and imported into IES-
VE-Pro to run an energy simulation of the current building configuration and then
testing it with hypothetical night flushing. Once night flushing has been incorporated in
the model and results have been generated, then measures can be taken to determine
how to improve night flushing’s efficiency and effectiveness. Measures to investigate
are the size and the material of the thermal mass, the mass’s heat capacity, modulating
solar heat gain with architectural features, and maximizing airflow. All performed test
69

will be cumulative, meaning that after the mass has been altered and simulated then
the next test will be performed in addition to the mass simulation. Improvements to one
feature of the building affect the others, so using this strategy will allow all of the
building features to perform with synergy.

4.1 – Hypothesis
The hypothesis of this report is that by implementing night flushing, the
Lakeview Terrace Library can reduce its total annual energy consumption in half without
jeopardizing the buildings overall thermal comfort. The expected results of modeling
night flushing in the building and running an energy simulation are that it can be
effective under certain circumstances. Whether the building was actually designed with
the intent of using night flushing is still unclear, but with architectural features in place it
seems to be a realistic possibility. When night flushing was attempted in the library, the
airflow in cubic feet per minute was insufficient. After the building is modeled to match
the buildings current performance, it will then be modeled with night flushing with the
current architectural features.
Multiple simulations will need to be run to test which architectural features need
to be altered or replaced to enhance the efficiency of night flushing. Parametric tests
that will be performed are changing the wall construction size and material to find the
most effective thermal mass for the library. Several methods are altering the thickness
of the wall and slab on grade concrete floor to 10 or 12 inches and investigating
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different types of light and heavyweight concrete so the heat capacity of the thermal
mass can be maximized. The shading techniques and window types of the building will
also be examined to reduce the solar heat gain of the library. By increasing the size and
depth of the shading devices and selecting a window that has a more efficient shading
coefficient (SC), the interior temperatures will be decreased and the night flushing can
be effective for a longer period of time. The lighting will also be investigated to reduce
the internal heat gain as well as the buildings lighting energy. The expected results of
altering the architecture by these methods are that the effectiveness of night flushing
will be maximized and rendered a true possibility. Night flushing will be effective for the
majority of the day, and the need for air conditioning will be greatly reduced.
An extremely important parameter that will need to be parametrically tested is
the schedule for when and how long the operable windows will be open to allow the
night time air to ventilate into the building. A fair assumption is that keeping the
windows open between the hours of 7 pm till 6 am will be an ideal time frame for
gaining peak cooling potential. This way the cool night air will have plenty of time to be
ventilated into the building and also be closed in an appropriate time so the building is
not too cold when the library is opened for occupants. To further evaluate night
flushing, the simulations will also show at what times of the year and day that night
flushing will and will not be effective. The assumption is that night flushing on a day to
day basis during the cooling periods can work from the time the library opens at 10 am
until approximately 2:30 pm to 3:00 pm. During the months of late July and August, the
71

assumption is that night flushing will be least effective due to extreme outdoor heat
during the day and night. The simulations will in the end be able to show the outdoor
temperature’s that allow night flushing to work. The expected results are that night
flushing will work when the exterior temperature during the day is approximately 85
degrees and the exterior temperature at night is 55 to 60 degrees. When the
temperature swing is not great enough between day and night, then the air conditioning
will need to be utilized. The simulations will demonstrate when this is the case based on
previously recorded weather data for the city of Sylmar, California. The final results that
are expected through running these series of simulations are that night flushing can be
successfully implemented into the Lakeview Terrace Library. This will result in reducing
the library’s total energy consumption, energy cost, and carbon footprint in half, thus
making a LEED Platinum building a more environmentally sustainable post occupant
building that it should have already been.

4.2 – Selecting a Simulation Tool

In order to most effectively simulate night flushing and thermal mass, three
software programs were investigated: TRNSYS, EnergyPro, and IESVE-Pro. All three
programs have the capability of modeling natural ventilation and material specific heat
capacity and take them into account when calculating and modeling energy
performance. The determining factors in selecting a program were the program’s
simulation efficiency, necessary input parameters, its effectiveness in simulating natural
72

ventilation with and without mechanical assistance, its ability to simulate thermal
comfort, ease of use, familiarity with the program, and the programs ability to show a
physical building model.
The first program that was chosen to be the simulation tool for this analysis was
TRNSYS. TRNSYS is a flexible tool designed to simulate the transient performance of
thermal energy systems. It is primarily used in the fields of renewable energy
engineering and building simulation for passive as well as active solar design. Its main
use is for HVAC analysis and sizing, multi-zone airflow analyses, electric power
simulation, solar design, building thermal performance, and analysis of control schemes.
TRNSYS was designed and is under continual development by the Solar Energy
Laboratory (SEL) at the University of Wisconsin-Madison. TRNSYS currently boasts a
graphical interface, a library of 80 standard components; add on libraries offering over
300 other components, a worldwide user base and distributors in France, Germany,
Spain, Sweden, Luxembourg, Switzerland, the United States, and Japan. TRNSYS is well
suited to perform detailed analyses of any system whose behavior is dependent on the
passage of time. Its main applications include: solar systems (solar thermal and
photovoltaic systems), low energy buildings and HVAC systems, renewable energy
systems, cogeneration, and fuel cells (TRNSYS 2009).
After testing TRNSYS, it was determined that it would not be the ideal program
to use for this study. An issue was TRNSYS’ lack of a visual model. The visual interface for
73

this program is flow diagram (Figure 4.2.1) that has a series of characteristics such as
building, ventilation,

Figure 4.2.1 – TRNSYS Flow Diagram

weather data, and cooling systems that are all connected by flow arrows that only
connect if the proper calculated inputs and outputs are inserted. This made it extremely
difficult to know if the building was modeled correctly. The program relies heavily on
mechanical and thermodynamic calculations and numbers that the user has to know
well. In order to fully understand what parameters to input into the program, there
must first be an understanding of calculations to generate the appropriate input to
obtain the output. The lack of an architectural model made this program too complex
and difficult to learn in a reasonable period of time, so it will not be used in this study.
EnergyPro is a comprehensive energy analysis program that can be used to
perform the following calculations: hourly energy analysis, heating loads, and cooling
loads for low-rise residential buildings using DOE-2.1E. The strength of EnergyPro is its
ease of use and ability to quickly generate an energy report and its compliance with or
74

against California Title 24. EnergyPro was the second choice to be the simulation
program. It was thought to be best suited to be the simulation program for this project
because the original energy simulation was done using EnergyPro. Yet, there were many
good reasons for not choosing this software program. It had a poor, non graphic model
input method. The software does not have the best capability to run night flushing. This
was shown through parametric tests that were performed to make sure that the
program modeled thermal mass correctly and when using thermal mass, the energy
consumption results and data had little effect (Table 4.2.1). The only way to model night

ANNUAL
LVT with R-13
Plaster Walls
LVT with 8" CMU
Thermal Mass
Electric Energy 169,463 kWh 168,932 kWh
Gas Energy 703 kWh 410 kWh
PV Energy 19,087 kWh 19,087 kWh
Total Energy
Consumption 151,079 kWh 150,255 kWh
Table 4.2.1 - EnergyPro Totals for Parametric Thermal Mass Tests
75

flushing is by altering the mechanical systems to act as natural systems, but when values
were entered at zero for fans and other mechanical systems to correctly portray natural
ventilation, the program would automatically assign a value. In the end, EnergyPro is a
solid program for testing if a building meets California Title 24, but its lack of a visual
model and its inability to accurately model thermal mass and natural ventilation ruled it
out as a possibility to be the simulation tool for this study. Night flushing is based on
natural ventilation and thermal mass and EnergyPro could not provide the simulations
needed.
“Virtual Environment-Pro (VE-Pro) is a building performance analysis software
program from Integrated Environmental Solutions (IES). The software allows the import
of a Revit model to perform building environmental analysis on. The Revit contains
information on geometry, materials, occupancy, climate and equipment. A variety of
different interconnected modules are available so users can build analyze different
sectors of their building. The building analysis categories are Energy/Carbon,
Light/Daylight, Solar, Natural Ventilation, Airflow/Computational Fluid Dynamics,
Value/Cost, Egress, Mechanical, Model Building, and Price/Purchase (IESVE 2009).
From preliminary research it appears that IESVE has a strong interface for
modeling night flushing and thermal mass. IESVE is the best choice for being the
simulation tool for modeling the library with night flushing. It has the visual architectural
model that can be imported from Revit, and it has the strongest ability to model energy,
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thermal comfort, thermal mass, natural ventilation, air movement, and night flushing,
while taking into account the unique geometry of the library’s form.
After several weeks of testing and learning TRNSYS and EnergyPro, it was
determined that they were not the best software programs for this thesis. IESVE-Pro
was selected and used to compare the building’s simulated energy and thermal
performance against the library’s originally designed energy simulation in EnergyPro and
the building’s current performance. All three programs can simulate and model night
flushing and thermal mass in different matters and with slightly different mathematical
formulas. TRNSYS was not used as the simulation tool mainly because it would take too
long to master. EnergyPro was used as the simulation tool for the library’s original
design and thus sets up a sensible comparison. IESVE allows for the building to be
accurately modeled architecturally. This allows the night flushing and thermal mass
simulations to give the most accurate energy and thermal comfort results based on the
building’s actual geometry. IESVE can also simulate the flow of air movement
throughout the building. With this software the amount of data that can be generated
will give the clearest and most thorough building simulation results for analysis.

4.3 – Building the Revit Model
In order to build an accurate Revit model, the architectural construction
documents were used to match the model as closely as possible (Figure 4.3.1). After the
model was constructed, spaces need to be identified, using the room tool in the building
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Figure 4.3.1 – Revit Exterior Renderings
in order to create zones to import into VE-Pro (Figure 4.3.2). Once the spaces have been
designated, then the Revit model is exported as a gbxml file so that VE-Pro could import
the 3D model. The most important aspect of creating the Revit model is accurately
modeling the interior spaces.

Figure 4.3.2 – Revit Floor Plan with Specified Zones
Modeling the exact areas, volumes, shapes, and window openings of the zones
will generate the most accurate model to import into VE-Pro. The main reading room
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(Figure 4.3.3) was the most important zone to model as accurately as possible to the
actual building dimensions. This is where the night flushing is taking place; the area of
the space is 5,135 SF and the volume is 98,660 cubic feet. These totals are almost
precisely what the actual building totals are, proving the geometric accuracy of the
model.

Figure 4.3.3 – Revit Main Reading Room Renderings
Revit was chosen as the program to create the original model in rather than
Sketchup and AutoCAD 3D because of the accuracy of the modeling as well as Revit’s
ability to create calculated bounded spaces. Through research of Revit and VE-Pro as
well as personal experience, Revit models have the least amount of errors when
transferring the information between programs using the gbxml file format.

4.4 – Matching IES-VE to Current Performance
The VE-Pro model was first thermally modeled to match the buildings current
performance. The reason for matching the building’s current performance as the first
step is setting up a realistic base case in order to use as an accurate starting point. The
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way the building was modeled to match the current building was first by importing the
Revit model. The model was the exact square footage and area for every room of the
library. The next was matching the construction of the building’s exterior walls, interior
walls, roof, flooring, and glazing. Then the internal loads of the building were input using
the data supplied from the original EnergyPro model, the library’s design intent manual,
and the building specifications. This includes the building activity type of each zone of
the library, ventilation flow rate, light and mechanical internal gains, the infiltration
rates, and the library’s occupancy rates. These are all needed to determine the library’s
internal heat gain. After all of the architectural data was input, the weather file is input
using the Sylmar weather data. The weather file is selected and then the buildings
latitude, longitude, and elevation are added. The next step was running the Suncast
solar simulation tool for the site. This determined the amount of sunlight the building
receives, as well as the amount of sunlight that is shaded which determine the building’s
solar heat gain. The last step was inputting the Apache System heating and cooling
system design information. Once all of this data was input into VE-Pro then the Apache
System Dynamic Simulation (within VE-Pro) could be run, the results of the simulation
generated the sensible heating and cooling loads per room. These results were
compared to the mechanical schedule and the EnergyPro model to make sure the loads
of the VE-Pro simulation matched the sensible cooling loads of the system’s fan coil
units. The numbers were very close, which proved that the library was modeled
accurately. The study could then be continued with the night flushing incorporated.
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4.5 – Implementing Night Flushing
In order to demonstrate that night flushing can be successful and productive in
the library, the library must first be simulated with night flushing using the current
building construction and conditions. The expected results of this test should prove that
night flushing cannot work as the building is currently designed. The actual library tried
night flushing and was unsuccessful so if the parameters are set properly, the initial
simulation should also fail. From the layout of the building, it makes sense for night
flushing to be used in the Main Reading Room which will be the main focus of this study,
but it will also be tested in the main bookstacks, the lobby, and the multi-purpose room.
For the smaller zones, it makes most sense to continue to use the fan coil mechanical
system for cooling. They simply do not have the area to successfully naturally ventilate.
Also, this simulation will not use the evaporative cooling tower as it was intended to be
used. Currently the tower’s louvered openings are closed, and tower is not in operation.
The simulation will treat the tower as another regular building zone. The simulation of
the library using night flushing with its current construction will serve as a starting point.
From here, a series of parametric tests shall be performed to see what architectural and
mechanical features can be altered or implemented in order to effectively incorporate
night flushing into the library.
The first two methods for increasing the performance of the night flushing are
enhancing the thermal mass (walls and floor) and determining different types of glazing
to improve the shading coefficients of the windows using the program Window 6.
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Windows 6 is a research program by the Lawrence Berkley National Laboratory that was
developed to model complex glazing systems. It uses a series of algorithms to calculate
the properties and parameters of glazing systems with the use of extensive libraries:
glass library, glazing system library, shading layer, and shading systems library. The third
method that will be used will be changing all of the lighting from incandescent to
fluorescents in order to reduce the solar heat gain. Another architectural method that
will be considered is altering the buildings shading to reduce the library’s solar heat
gain. If night flushing is still not effective then a hybrid system will be used by using
mechanical fans to increase the amount of air entering the building in cubic feet per
minute. The final method to maximize night flushing will be testing different operable
window schedules. Knowing when and how long to leave the windows open at night will
directly affect the interior temperature.
The final stage of the simulation process will be incorporating the fan coil system
to cool the rooms and zones of the building that night flushing was not appropriate. The
system will also be used in the event that the interior temperature and percentage of
people dissatisfied is too high in which case mechanical cooling will be needed. This will
complete the simulations process and in the end will determine the buildings thermal
comfort level as well as the total energy consumption for the Lakeview Terrace Library.
The next step will be to analyze the data and compare it to the buildings current
performance and original design.

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Chapter 5: Original Building Design and Performance
Documentation from the Lakeview Terrace Library’s design phase will be crucial
to understanding the library’s original design intent. The design data will set up the first
stage of the library’s performance comparison. Understanding how the building was
intended and planned to perform will set up a controlled variable. From this base case,
it can then be determined what has changed in the post occupancy stage to lead to the
library’s present day performance. The library was built based on the architectural
design and energy assumptions generated in the design phase.

5.1 – Architectural Construction Documents
The library’s original construction documents (Appendix A) were used to
accurately architecturally model the building as a BIM model in Revit. The main floor
plan (Figure 5.1.1), sections, elevations, details, schedules, and building specifications
were used. The most important aspects for night flushing are the thermal mass, the
operable windows, and the internal and external heat gains. When modeling the
building, it is crucial to accurately model the walls and the window openings. The wall
section (Figure 5.1.2) is extremely valuable in order to understand the construction of
the thermal mass walls and floor as well as what type of concrete is used and what the
heat capacity and R-Values of the walls are. The concrete specifications indicate that
the exterior walls and interior walls are made of lightweight CMU blocks to ASTM
standards, and the floor is a medium weight slab on grade exposed concrete floor.
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Figure 5.1.1 - LVT Main Floor Plan Figure 5.1.2 - LVT Exterior Wall Section

The window schedule and specifications provide the necessary data needed to
correctly model the windows and their SHGC values, glazing, and U-values. The
motorized window control systems are to operate awning windows located in the main
reading room and lobby, and it will be integrated into building’s HVAC and Electrical
systems. The system is manufactured by Clearline Inc. It includes the motor, nominal
voltage: 120V 60Hzcycle single phase and 2.8 amps, built in limit switches, emergency
manual override, 3 position switch, and aluminum screening.
All exterior glazing is currently double-glazing, with argon gas fill. Glazing layers
are spaced ¾” apart using low-conductance spacers with thermal breaks. Allowable gas
leakage cannot exceed 0.5% per year. South-facing glazing (lower windows), north-
facing glazing and east-facing glazing are spectrally selective, low-e coating; T
vis
=0.70+ at
center of glazing. The South-facing glazing (upper windows) are clear. The west-facing
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glazing is low-transmission and low-e coated. As far as air Infiltration, the windows and
doors provide adequate weather stripping to prevent infiltration and exfiltration, and
the air-leakage rating cannot exceed 0.15cfm/ft
2
.
The lower south-facing windows have a Low-E coating, a visible transmittance
(T
vis)
of 0.70, a U-factor of0.25, a shading coefficient (SC) of0.42,and a solar heat gain
coefficient (SHGC) of 0.37. The upper south-facing windows are clear with Low-E
coating, T
vis
= 0.80, U-factor = 0.49, SC = 0.89, and the SHGC = 0.76. The north-facing
windows have a Low-E coating, T
vis
= 0.70, U-factor = 0.25, SC = 0.42, and the SHGC =
0.37. The east-facing windows have a Low-E coating, T
vis
= 0.70,U-factor = 0.25, SC =
0.42, SHGC = 0.37. The west-facing glazing have a Low-E coating, low-transmission, T
vis
=
0.50, U-factor = 0.25, SC = 0.38, and the SHGC = 0.33.

5.2 – HVAC Design Intent
The mechanical schedules (Appendix B) and HVAC design intent describe how
the building was engineered to be cooled. The schedules provide the type of systems
the library uses in its HVAC system as well as all of the fundamental data inputs. This
data was used in order to model and simulate the buildings current cooling and heating
loads. The most valuable information from the mechanical plan (Figure 5.2.1) is the
location of fan coil units and what zones of the building they serve. There are nine total
fan coil unit for the zones of the building: The multi-purpose room, the lobby, the main
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bookstacks, the staff work zone, the teen reading area, the three main reading room
zones, and the storytelling area.

Figure 5.2.1 - Mechanical Plan

The HVAC system consists of a central chiller with a pump for cooling and a
central boiler with a pump for heating. At the zone level, temperature is controlled by
the use of fan coils provided with chilled water and hot water heating coils. When
heating or cooling are needed, zone control valves in the hot water and chilled water
piping to the fan coils will open. Fan coils are provided with economizers to provide free
cooling when the outdoor air temperature is sufficiently low to meet space
requirements.
The sequence of operations for the fan coil units state that the system will be
initiated by the zones thermostat in conjunction with PCM controls modulating the
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chilled water and hot water control valves in sequence to meet the desired zone
temperature. When the outside air temperature is lower than the return air
temperature, the fan coil system will be deactivated and automatic windows will be
opened. When the zone temperatures reach the upper limit set points, the windows are
closed and the fan coil system will be activated to economizer mode and mechanical
cooling mode in sequence to maintain zone temperature. When the temperature
reaches the lower limit set points, the windows are closed and the fan coil system will
return to economizer and mechanical heating mode in sequence to meet the zone
temperature. The economizer cycle is set up to override the demand control ventilation.
The motorized windows were actually designed to remain closed during off business
hours; if they are opened then alarms will sound. This shows that night flushing was not
a part of the original design.

5.3 – EnergyPro Simulation
The EnergyPro simulation is the final energy modeling simulation that
GreenWorks used to show how the building would perform, its total energy
consumption (Table5.3.1), and its compliance margin of 59.5% with California Title 24.
The energy model was used in the final documents and met the Title 24 standards for
building energy compliance. The EnergyPro simulation provided the designed energy
total which was used to compare to how the building is currently performing and how it
will perform with night flushing. The model supplies lighting intensity data, which was
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used to determine how to reduce the internal heat gain from the interior lighting. The
EnergyPro model also provides an annual sources energy summary, an envelope
compliance summary, a mechanical systems certificate of compliance, a mechanical
system and equipment summary, a utility incentives worksheet, annual site energy,

Table 5.3.1 - LVT EnergyPro Annual Site Energy Use

and an energy use and demand summary. Also, by having access to the original energy
simulation of the library, all of the inputs and outputs of the simulation were studied
and reviewed to understand how the library was designed to perform. The final energy
consumption totals for the EnergyPro original design simulation are:
Electricity Energy 130,706 kWh
Gas Energy Generated 344 Therms x 29.3 Conversion Factor = 10,079 kWh
PV Energy Generated - ( 19,087 kWh)
Total Energy Consumption 121,698 kWh
Cost per kWh $0.12/kWh
Energy Bill $14,603.76
Table 5.3.2 – LVT EnergyPro Energy Totals
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5.4 – Solar Study
During the design of the library, solar studies were conducted using Ecotect to
determine the amount of sunlight the building would receive and from what angles.
Using the library’s latitude, longitude, and site elevation the study was able to simulate
the path of the sun in relation to the library for every month of the year (Appendix C).
The solar study helped to determine how much shade the building would need to keep
the building from overheating thus needing more air conditioning. The solar study
results were needed in order to help determine how much more shade can possibly be
added to the building and where the shading can be added to further reduce the heat
gain from the sun. Knowing the sun’s movement and its effect on the library will be
critical in enhancing the shade. With night flushing, heat gain needs to be minimized as
much as possible so during the day the mass does not have to absorb as much heat.
August is the peak month for high California temperatures, so the solar study (Figure
5.4.1) of the library for the month of August is the most important month to analyze.

Figure 5.4.1 - August 1
st
Solar Diagrams

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5.5 – Annual Solar Power Generation
In order to accurately compare the library’s designed energy consumption versus
its current energy consumption, the annual solar power generation from the library’s
photovoltaic cells needs to be calculated. The original EnergyPro simulation cannot
model solar power generation, so the simulation’s energy consumption is actually
higher than the total would be with the PV cells integrated. The roof of the library has
46 PV panels with a DC rating of 11.4 kW tilted at 22°, the library entrance trellis has 14
PV panels (Figure 5.5.1) with a DC rating of 1.87 kW tilted at 5°. The Lakeview Terrace
Facilities manager, Juliana Chang, does not have access to any actual data for how much
solar power the Panels actually generate. So, in order to determine how much energy
the panels could generate, the PV data will be plugged into a performance calculator

Figure 5.5.1 Entrance Trellis PV Panels

for grid connected PV systems. The site that was recommended by Chris Buntine of
GreenWorks Studio to roughly estimate the PV energy generation is
(http://rredc.nrel.gov/solar/codes_algs/PVWATTS/version1/). With the data generated
from the PV Watts site, the energy generation in kWh can then be subtracted from the
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EnergyPro simulation to give a more accurate total of the library’s designed energy
consumption.
The solar panel rooftop array, according to the building specifications, consists of
46 field applied roof panels by Uni-Solar’ PVL-128 and 10 field applied roof panels by
Uni-Solar’ PVL-64.The system provides peak kilowatts of 11.14 kWdc at Standard Test
Conditions. The solar electric roof mounted system consists of a metered grid-tied
system of a solar electric roof mounted array, supports, combiner box, inverter, DC/AC
disconnects, ground fault protector, ground conductors and connections, conduit and
wiring. Modules, inverters and all necessary accessories are in compliance with
California Energy Commission Renewable Energy Buy Requirements. The system
operates at 120 volts. The panels are field applied roofing laminate panels that are
15.5”x 18’, bonded to 16”wide flat galvalume pans. The total energy generated by the
system is calculated to be 17275 kWh of electricity (Table 5.5.1).

(Table 5.5.1 - Solar Panel Data for Rooftop PVC’s)
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The solar panel trellis array covers the entrance trellis area and consists of panels
by Atlantis Energy, Inc. The system provides peak kilowatts of 1.876 kWdc at Standard
Test Conditions. The trellis system is made up of 14 modules that are each composed of
three laminated glass layers with photovoltaic cells and EVA under the top layer and
PVB above the bottom layer. The glass layers are tempered and heat strengthened to
meet safety glass requirements and are approximately 44” x 47 1/2'” x ½” thick. The 64
cells with the modules are 5” square with corners removed and 3/8” spacing. They are
manufactured by Siemen’s as single crystalline silicone that collectively produce over
134 Wdc per module. The translucency per module is 25.4 %. The total energy
generated by the system is calculated to be 2532 kWh of electricity (Table 5.5.2).

(Table 5.5.2 - Solar Power Data for Trellis PVC’s)
The total amount of AC Energy from solar power for the entire library is
simulated at 19,087 kWh annually. This number is a rough calculation based on average
amounts of insolation values generated for the San Fernando, California area. The
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building was unable to provide the amount of energy they were generating from solar
power, so calculating a rough estimate was the best option for gathering an idea of the
buildings total energy consumption minus the energy generated from solar power.

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Chapter 6: Current Building Performance
Documentation on how the Lakeview Terrace Library is currently performing is
critical in analyzing the building. The current energy consumption data will set up the
second stage of the library’s performance comparison. The data gathered from the
building’s energy and gas bills can be directly compared to how the building was
designed. This comparison will show whether the building is performing better than it
was designed for, which is unlikely. The current data also is the base case from where
improvements will be made from. A building can be designed to be perfect, but in real
time there are events and circumstances that occur that alter this course. This
investigation will look to discover why the building is acting how it is and how to
improve it. This chapter will present the data that shows how the building is currently
functioning and performing in terms of energy consumption.

6.1 – Energy and Gas Consumption Bills
The energy and gas consumption bills are the key pieces of information for the
analysis of the library’s current performance. The data from the energy bill (Table6.1.1)
is how much total site energy the building consumes a year in kilowatt hours (kWh),
how much it consumes per month, what the library’s yearly energy consumption cost is,
and how much it costs per kWh. The bill also provides the high peak, low peak, and base
period consumption totals for the year as well as bimonthly. These totals can be
compared to the high peak, low peak, and base period demands in kilowatts per month
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and by year. The totals will tell how much energy is being consumed during Los Angeles
peak electrical hours, which play a direct effect on cost incentives as well as price per
kWh.

Table 6.1.1 - LVT 2008 Electricity Consumption Bill

This focus of this thesis is on site energy and not source energy. Site energy is the
energy consumed by the on-site building system. Source energy accounts for the energy
needed to produce and transfer electricity to the building location. Site energy is
generated from the source energy at roughly 30% efficiency. This acknowledges that it
takes three times the energy to generate and transport 1 kWh of site electricity. 1 kWh
equals 3143 BTU’s of heat, so roughly 1 kWh of site energy represents about 10,000
BTU’s of source energy or the equivalent of 3 kWh. So, the actual source electrical
energy for the Lakeview Terrace library would be 1,254,580,000 BTU’s, equivalent to
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418,193 kWh, to produce the on-site energy of 125,458 kWh (30% of the source
energy).
The data from the gas bill (Table6.1.2) is the total 2008 gas consumption of the
library in therms. Therms can be theoretically converted to kWh by multiplying by the
conversion factor of 29.3 kWh per 1 therm to achieve on-site energy; this will allow the
gas and the electricity site totals to be combined to give the total energy consumption in
kWh for the building. It is recognized that natural gas is delivered to the building site at a
high efficiency, so unlike electricity there is a minimal difference between site and
source energy. The rest of the data from the gas bill is gas consumption per month, the
annual gas consumption cost, and the cost per therm.
Lakeview Terrace Library - Gas Consumption FY 08

Billing
Period
Therms
used
Amount
billed
January 2008 433 493.50
February 2008 313 358.22
March 2008 271 292.03
April 2008 195 199.96
May 2008 85 96.84
Jun 2008 89 102.26
July 2008 10 34.97
August 2008 25 59.53
September 2008 40 75.55
October 2008 43 73.69
November 2008 25 46.17
December 2008 166 205.23
TOTAL 1,695 $2,037.95
Table 6.1.2 - LVT 2008 Gas Consumption Bill

The current building performance data is what the building simulation model in
Virtual Energy Pro will be compared to. The main focus of incorporating night flushing
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will be to reduce the buildings’ current electricity consumption used for mechanical
cooling. The library’s energy bill has already incorporated electrical energy conservation
from the PV system. The final energy consumption totals for Lakeview Terrace Library’s
current performance are shown in the following table:
Electricity Energy before
PV System Conservation
125,458 kWh +19,087 PV Energy = 144,545 kWh
Gas Energy Generated 1,695 Therms x 29.3 Conversion Factor = 49,664 kWh
PV Energy Generated - ( 19,087 kWh)
Total Energy Consumption 175,122 kWh
Cost per kWh $0.12/kWh
Energy Bill $20,208.11
Table 6.1.3 – LVT 2008 Energy Totals

The library’s facility manager was not able to provide how much of the total
energy consumption was from cooling. In order to gather a rough assumption, building’s
cooling energy is on average 32% of the buildings total energy consumption. So to
generate a rough estimate of how much energy the cooling of the Lakeview Terrace
Library possibly consumes, the total energy consumption in 2008 of 175,122 kWh can be
multiplied by 0.32. The rough estimate of cooling energy consumption is about
56,039.04 kWh. This total will not be used in any further calculations; it is primarily to
give an approximation of how much energy the cooling of the library consumes.

6.2 – Energy Management System
The library’s building automation system (EMSC) is a Johnson’s Controls fully
direct digital control system with the ability to monitor and control the HVAC equipment
as well as the operable windows. This is a permanent on-site computer terminal located
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in the electrical room that relays the data to the City of Los Angeles, Department of
General Services. The EMCS fully controls, enables, and disables different points of the
HVAC equipment. It provides the following energy conserving control strategies: hot
water reset, night ventilation purging, CO2 outside air reset, full trending capabilities,
time scheduling, alarm instructions, economizer, run time, and event program. After a
meeting with the Department of General Services it was revealed that the data and
temperature trending of the EMSC system was never set to record. The software for
trending the controls is in the computer system, but no parameters were set, so no
trending data has been recorded. All it would have taken was someone to input the
desired data to trend and length of time, and the system would have a kept a log and
graph of the data.
The EMSC data (Appendix D) that is available provides the set-points for the
mechanical systems of the building, most notably the chiller, boiler, and nine fan coil
units. The data is useful in determining how the building’s equipment is currently set to
run and how the controls dictate when the systems are turned on and off and at what
power. The data also reveals the current HVAC schedules for what hours of the day,
week, and year the systems are set to operate and turn off. Figure 6.2.1 is the data for
fan coil unit 3 in the main reading room, the zone in which night flushing will be
implemented. The current conditions of the zone have the cooling set to 73.5 °F while
using an outside air temperature of 70.8 °F for early October. The challenge in using
natural ventilation is trying to match these conditions without mechanical assistance.
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Once night flushing is in use, the fan coil temperature sensor will be set to 76°F. The fan
coil unit will only be activated when night flushing can no longer keep the interior
temperature below 76°F.

Figure 6.2.1 - EMSC Fan Coil 3 Data for the Main Reading Room

6.3 – Sylmar Weather Data
The city of Sylmar has a weather station, the KCASYLMA2, approximately 3 miles
west of the library (Figure 6.3.1). The weather station sends all of its data directly to the
weather site, Wunderground.com. The weather station gives charts and graph
documenting weather data for Sylmar including temperature, dew point, humidity, wind
speed, wind gust, wind direction, pressure, and precipitation (Figure 6.3.2). The most
important aspect of the weather data will be the data on wind patterns and
temperature swings of the climate. It is important to know the wind patterns and the
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temperature swings of Lakeview Terrace in order to determine how much air the
building can draw and how much air needs to be draw in to make up for the

Figure 6.3.1 - Sylmar, CA Weather Station Location

temperature during the day. The night time temperature is also important to know to
determine the incoming air temperature. The humidity of the area will also be
important because night flushing is ineffective in humid areas.

2009 Annual Sylmar Weather Data
High Low Average
Temperature 105.3° F 33.1° F 66.1° F
Dew Point 66.8° F ¯ 2.2° F 38.8° F
Humidity 98.00% 4.0% 45.6%
Wind Speed 26.0 mph from the NW ¯ 5.6 mph
Wind Gust 36.0 mph from the NW ¯ ¯
Wind ¯ ¯ South
Pressure 31.01 in 27.2in ¯
Precipitation 10.67 in ¯ ¯
Table 6.3.1 - 2009 Annual Sylmar Weather Data

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Figure 6.3.2 - 2009 Annual Sylmar Weather Data

The weather station has recorded weather data for Sylmar, California, dating
back to January 1
st
, 2006, this will help in understanding the weather trends of the area.
This study will use the data from the 2009 calendar year to match the energy bills of the
library, which are also from the year 2009. The most valuable information for this study
is weather data the cooling months (Appendix E) in Sylmar, California from July to
October. Weather data can be displayed daily, weekly, monthly, and annually. The daily
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data will be beneficial in determining the diurnal temperature swings during the months
of the cooling season, which is necessary for night flushing.
In order to make sure natural ventilation was possible for the climate of Sylmar
California, Climate Consultant 4’s psychrometric chart was used for San Fernando,
California, in which Sylmar is a district of (Figure 6.3.3). The data gathered from the
psychrometric chart is relatively similar to the Sylmar weather data from
Wunderground.com. The Sylmar data had peaks of high and lows that varied from the
chart, but both sets of data gave similar results. The chart shows that for at least 30 % of
the occupied hours of the library, the exterior temperature is greater than 60°F and less
than 80°F and the relative humidity is less than 70°F. The library is occupied for 2496
hours of the year, and 30% of that time frame is 748.8 hours. The chart also shows that
the exterior temperature for San Fernando, California, is below 68°F and 70% RH for
6297 hours of the year, and for many nights it is below 68°F for more than 8 hours. The
climate also shows that it is only over 80°F for 140 hours of the year, and the outside air
dew-point is less than 64°F throughout the year. This exterior climate data on
temperature and humidity make it possible for night flushing in the specific San
Fernando / Sylmar region of California.
The wind flow of the area around the library is typically coming from the
southwest as shown in the wind rose diagram (Figure 6.3.4). Summer wind velocity is
typically 6.71 to 13.42 mph. The diagram shows the wind flow on August 31
st
, one of the
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Figure 6.3.3 – Psychrometric Chart for California Climate Zone 9

peak cooling days for the summer months of Sylmar, California. The library’s orientation
allows the outside wind to flow through the building from south side operable windows
of the main reading room through the north side windows and into the courtyard. The
orientation of the building in comparison to the direction of the wind makes it appear
that the library was more interested in bringing the cool air through the building for the
courtyard then supplying the air to the evaporative cooling tower.

Figure 6.3.4 – LVT Exterior Wind Rose
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6.4 – Monitoring Indoor and Outdoor Climate Data with Data Loggers
A HOBO is a datalogger device that is used to measure a wide range of
parameters including temperature, wind, humidity, and light intensity. HOBO’s were
used in this report to record indoor and outdoor temperature and humidity data at the
Lakeview Terrace Library (Appendix F). The data was analyzed to look for any odd
temperature trends in 10 different areas inside the library and 2 different locations
outside the library (Figure 6.4.1). By setting up twelve different HOBO’s, the difference
in interior temperature data for the different areas of the library can be evaluated and
compared.
Before the HOBO’s were installed, they had to be normalized to make sure they
all worked properly and were all gathering similar data. The results of the normalization
are shown in Appendix A. All of the HOBO’s were very similar and the data they
collected were all consistent. So there were no wild or peculiar variances. The data
loggers were set to collect data for every minute for 4 hours and were placed in the
refrigerator, a space that had a constant temperature and humidity. By normalizing the
HOBO’s, they were then ready to be installed in the library without worrying about any
type of prior errors.
The HOBO’s are 2.5 inches x 2 inches x 1 inch and weigh 0.9 ounces (Figure
6.4.2), so they are very small and compact, making them easy to install in areas of the
library in which they go unnoticed and re less of a target for theft. When the HOBO’s
were installed at the library they were installed for the dates of 10/28/2009 till
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11/07/2009. They were set to record temperature and relative humidity every 10
minutes. The twelve locations of the HOBO’s were chosen based on different factors.
The two outdoor HOBO’s were raised to a height of 5 feet out in an open space in front
of the library. The outdoor temperature sensors are not accurate if they are hit by direct
sunlight, so a transparent mechanism was created to protect the sensor from direct sun
rays, rain, and other environmental factors. HOBO 3 was placed 10’ high on the north
wall of the main reading area to determine the temperature on the opposite side of the
reading room that is not right in the path of the sun all day. HOBO 4 was placed at 4’ on
the

Figure 6.4.1–Data Logger Placements Figure 6.4.2 - HOBO Data Logger

north wall of the main reading room to compare the difference in data to HOBO 3, and
see what the change in temperature is from the working plane to the ceiling. The same
was done for HOBO’s 5 and 6. HOBO 7 was placed in the south of the bookstacks at an
elevation of 7’ , to compare to HOBO 8 which is in the north of the bookstacks also at 7’.
They were placed in these locations to see how the temperatures vary as air moves
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north through the building into an area only 8 feet high compared to the main reading
room which has a roof with a 22 degree angle starting at 28 feet. HOBO 9 was placed at
the entrance at 2 feet; this will show the temperature in the building as people enter as
well as the variances in the data as the doors open. HOBO 10 is in the auditorium/class
room at 2’ or desk level, it has a high sloping ceiling and is seldom used. HOBO 11 is at 7’
high in the cooling tower, and HOBO 12 is at 2’ in the tower. They are being used to
determine the temperature difference as air is coming down and out of the tower.
The results of all of the data loggers showed no irregularities in any of the
spaces. Air temperatures were within two to three degrees of the HVAC systems set
temperature ranges.
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Chapter 7: Night Flushing Simulation Data and Results
7.1 – Matching IESVE-Pro Model to Current Building Performance
When a building model is imported into an energy modeling program there are
always errors that need to be corrected with the building’s volume, openings, skin, and
potential points of infiltration. When the Revit model of the Lakeview Terrace Library
was imported into IES Virtual Environment Pro, there were several walls and window
openings that did not survive the transfer between programs. VE-Pro offers a building
modeler called BuildingIT that allows the user to fix errors in the building envelope.
After modeling in the missing walls and windows the library’s geometry was completely
repaired and ready for the construction materials to be applied. The final 3D model
(Figure 7.1.1) and floor plan (Figure 7.1.2) accurately matched the geometry and design
of the original Revit Model. After the geometry was correct, the next step was inputting
the construction details, thermal conditions, weather data, and generating the room
loads (Appendix G).

Figure 7.1.1 – VE-Pro Model Figure 7.1.2 – VE-Pro Floor Plan

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Once the building’s geometry was accurately finished and all points of
penetration were sealed then the next step was assigning the construction details in VE-
Pro. Modeling the thermal mass is extremely important. The design specifications were
used to make sure all material parameters of the model were correct. The exterior wall
was modeled using a three inch exterior insulation finishing system (EIFS) as the
outermost layer. It has a conductivity of 0.243 BTU in/hr.ft², a density of 1.561 lb/ft²,
and a specific heat capacity of 0.3344 BTU/lb °F. The second and last layer of the
external wall was an eight inch interior exposed lightweight CMU wall. The concrete has
a conductivity of 16.0 BTU in/hr.ft², a low density of 74.914 lb/ft², and a specific heat
capacity of 0.2388 BTU/lb °F. The total exterior wall in VE-Pro was calculated as having a
total R-Value of 12.8624. The actual exterior walls of the library are eleven inches and
have a total R-Value of 13, so the modeled walls are accurate. The interior wall uses the
same type of exposed CMU as the exterior wall. The only difference is that it is an eight
inch thick wall instead of eleven inches. The exposed slab on grade concrete floor uses a
six inch medium weight concrete with a conductivity of 9.707 BTU in/hr.ft², a density of
118.613 lb/ft², and a specific heat capacity of 0.2388 BTU/lb °F. The 21’6” roof is an
eight layer construction. It consists of steel siding, plywood sheathing, polystyrene
insulation, another layer of plywood sheathing, a layer of R-30 insulation, galvanized
sheet metal, a six inch air cavity, and mineral fiberboard acoustical tile. The total R-
Value of the modeled roof was 47.3236 ft² hr. °F/BTU compared to and R-Value of 48 for
the actual library. After the double pane low e glazing with an argon filled cavity was
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modeled, VE-Pro derived glazing parameters. The modeled window had a U-Value of
.2608 BTU/ft² hr. °F and a total shading coefficient of .4407, the actual library windows
average a U-Value of .25 and a shading coefficient of .44.
The thermal conditions of the building are the next step in matching the models.
Using the building template manager, the first step is assigning building regulations to
all twenty one rooms of the library. Each room is defined as a heated or occupied
space, an NCM building type of library, museum or gallery, and then each room is
assigned an activity type. The main reading room is defined as an open office plan with
an activity level of 70. The second step is applying room conditions to each zone. This
sets the simulations heating and cooling set points’ for the library they are set at 68° F
and 74° F. The third step is setting the systems outside air supply minimum flow rate
and HVAC system preliminary data. The fourth step is inputting the internal gains data.
The three types of internal gain are lighting, occupancy, and machinery. The lighting
types used in the library are fluorescent and incandescent. After the lighting sensible
gains were input, the lighting profile schedule was set (Figure 7.1.3). The fifth step is

Figure 7.1.3 – LVT Lighting/Occupant Schedule
109

identifying the infiltration rate. The library was designed for a max infiltration flow rate
of 0.5 air changes per hour. The thermal conditions of the building (Table7.1.1)
combined with the external heat gain and the weather data of Sylmar will be used to
determine the cooling loads of the building.
Room Room Type
Min. Flow
Rate
(CFM/ft²)
FCU
Lighting Sensible
Gain (W/ft²)
Occupancy
(ft²/person)
Machinery
(W/ft²)
Main Reading
Room - 1
Open Plan
Office 0.3 1 Tungsten - 3.01 50 N/A
Main Reading
Room - 2
Open Plan
Office 0.3 2 Tungsten - 2.823 50 1.5
Main Reading
Room - 3
Open Plan
Office 0.3 3 Tungsten - 2.823 50 1.5
Main Reading
Room - 4
Open Plan
Office 0.3 4 Tungsten - 2.823 50 1.5
Main Reading
Room - 5
Open Plan
Office 0.3 5 Tungsten - 3.551 50 1.5
Main Bookstacks Display Area 0.15 6 Tungsten - 1.7 100 N/A
Mech. Room Plant Room 0.15 6 Tungsten - 1.5 300 1.5
Electrical Room Plant Room 0.15 6 Tungsten - 1.5 300 1.5
Staff Workroom
Open Plan
Office 0.14 7 Fluorescent - 0.55 100 1.5
Staff Lounge
Common
Lounge 0.14 7 Fluorescent - 0.725 70 1.5
Staff Storage Storage 0.14 7 Fluorescent - 0.357 300 N/A
Staff Restroom Toilet 0.14 7 Fluorescent - 1.0 100 N/A
Head Librarian's
Office Cellular Office 0.14 7 Fluorescent - 2.0 100 1.5
I.T. Room Cellular Office 0.14 7 Fluorescent - 0.361 300 6.0
Custodial Office Small Workshop 0.14 7 Fluorescent - 0.638 100 N/A
Multi-Purpose
Room Open Plan office 0.9 8 Tungsten -2.25 16.7 1.0
Evap. Cooling
Tower Display Area 0.14 9 Fluorescent - 1.0 100 N/A
Lobby/Entrance Reception 0.21 9 Tungsten - 0.91 70 N/A
Lobby Storage Storage 0.14 9 Fluorescent - 0.357 300 N/A
Main Restrooms Toilet 0.15 9 Fluorescent - 1.106 100 N/A
Table 7.1.1 – Thermal Conditions
In order for VE-Pro to generate and calculate the solar heat gain of the library,
the weather data file for Sylmar, SanFernandoTMY2.fwt, has to be loaded into the
110

model’s virtual environment. The virtual environment tool consists of three stages in
order to accurately model the library’s outdoor climate. First, the building’s location
and site data (Figure 7.1.4) are input into the model. The location is selected from VE-
Pro’s site selection tool, and then the library’s latitude, longitude, and altitude are input:
latitude of 34.27° N, longitude of 118.4° W, and an altitude of 1067.9 ft. Second, design
weather data (Figure 7.1.5) info is entered which then generates cooling load weather
data for the select region. Third, the Apache simulation weather data file is selected. For
the library, the program was able to use the SylmarTMY2.fwt data file that was loaded
into VE-Pro.

Figure 7.1.4– Sylmar Site Data Figure 7.1.5 – Sylmar Site Weather Data

The weather file is used to model the climate as well as the library’s location in
relation to the sun. The Suncast solar shading analysis tool takes the location and site
data and calculates the sun’s affect on the model. The analysis generates a solar time
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(Figure 7.1.6 – Sun Path Diagram Figure 7.1.7 – Shading Analysis
graph, a sunpath diagram (Figure 7.1.6), solar shading calculations, shading visual
analysis (Figure 7.1.7), and the library’s solar gain. Solar heat gain for the building
(Figure 7.1.8) is on average 14,290 BTU’s/hr and the peak value is 81,957 BTU’s/hr at
11:30 am on Dec 20
th
.

Figure 7.1.8 - LVT Solar Heat Gain
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It is important to compare the VE-Pro weather file for the San Fernando Valley
region of California to the Wunderground weather data for Sylmar and to the California
climate zone 9 EPW file from Climate Consultant (Table 7.1.2). By comparing these
weather tools to the VE-Pro weather file, it will give a strong idea as to how accurate the
weather data will be for the simulation in comparison to what the building is actually
experiencing. This will give the building its due, because the VE-Pro weather data is
comprised of a series of climate averages from the San Fernando region over the years.
The Wunderground weather data from the Sylmar weather station gives the most
accurate weather data from what happened in the region in 2009. Its weather station is
located closer to the site than the VE-Pro weather file and Climate Consultant’s. It is
recognized that weather files and simulations can only simulate past weather data and
Weather Source
VE - Pro
Weather File
Wunderground 2009
Weather Data (Temp)
Climate Consultant
EPW (Temp)
Location San Fernando Valley, CA Sylmar, CA California Climate Zone 9
May
Temp. High (F) 88.9 96.4 92
Temp Low (F) 51.8 53.8 53
Temp. Average (F) 62.6 67.5 64
June
Temp. High (F) 91.0 104.1 93
Temp Low (F) 54.0 53.4 57
Temp. Average (F) 63.8 69.5 68
July
Temp. High (F) 90.1 100.4 96
Temp Low (F) 59.0 59.4 61
Temp. Average (F) 72.6 78.1 73
Aug
Temp. High (F) 94.0 99.8 97
Temp Low (F) 59.0 60.3 62
Temp. Average (F) 70.2 78.4 73
Sep
Temp. High (F) 95.0 99.4 102
Temp Low (F) 57.9 57.2 59
Temp. Average (F) 67.9 76.1 71
Table 7.1.2 – Weather Source Comparison
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trends and cannot predict and simulate future weather. So the best way available to
simulate the library is to understand and use the weather data that has been collected
from previous years. It is the best way to evaluate the exterior climate.
For the most part, all three sets of weather data for the summer months are
fairly constant and there is never a temperature difference greater than 10°F except for
the high temperature in June. The VE-Pro weather file never peaks above 100 degrees
like the Wunderground file does in July and the EPW does in September. The summer
temperature peaks for the simulation are not quite as high as the Wunderground and
EPW data have recorded for any of the months, so the peak temperatures for the
simulation are slightly lower than some of the data collected in the past which is typical
for averaged weather data. The temperature lows and averages for all three data sets
seem to be extremely close in values. When evaluating the library it is understood that
the actual library has experienced temperatures slightly higher than the simulation’s
averaged weather data has calculated, but the consistency of the average outdoor
temperature gives validation to the simulation. Since simulation weather files are
averages of the regions climate, it often leads to extreme temperature highs lows being
lower than what the region has actually experienced in the past.
The value of this comparison is in understanding that weather files vary based on
location, averages, and year. The best way to have evaluated the weather and climate
data of the library would have been to set up a weather station at the actually library
location for an entire year. If future studies are done on the Lakeview Terrace Library, it
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would be beneficial to set up data loggers on site and document the site data. For this
study, the VE-Pro weather file for San Fernando will be used, but it is understood that
the temperature highs can actually exceed 100°F in the summer months. This gives the
building some credit for having to experience higher temperatures than what VE-Pro
simulation can model as well as the EnergyPro model from the original design
simulation.
Now that the building has been modeled, the thermal conditions have been
input, the weather data has been applied, and the solar heat gain has been calculated,
the last step to determine the accuracy of the model is to calculate the library’s cooling
Room FCU
VE-Pro - Peak Sensible
Cooling Load (BTUH)
FCU - Sensible
Cooling Load
(BTUH)
Total VE-
Pro Cooling
Load
Total FCU
Cooling Load
Main Reading Room Zone 1 1 22705 25600
123144 149900
Main Reading Room Zone 2 2 26635 32600
Main Reading Room Zone 3 3 26799 32600
Main Reading Room Zone 4 4 25441 32600
Main Reading Room Zone 5 5 21564 26500
Main Bookstacks 6 18105 -
21478 26600
Mech. Room 6 1798 -
Electrical Room 6 1575 -
Staff Workroom 7 10368 -
23759 24600
Staff Lounge 7 3854 -
Staff Storage 7 833 -
Staff Restroom 7 1168 -
Head Librarian's Office 7 2089 -
I.T. Room 7 4924 -
Custodial Office 7 523 -
Multi-Purpose Room 8 41816 67200
62461 67200
Evaporative Cooling Tower 9 4323 No Cooling
Lobby/Entrance 9 9317 No Cooling
Lobby Storage 9 541 No Cooling
Main Restrooms 9 6464 No Cooling
Table 7.1.3 – Cooling Loads Comparison
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loads. VE-Pro has generated the cooling loads for each room based on all of the data
previously input into the building model. The loads from each room were relatively
similar to the sensible cooling loads that the mechanical fan coil units were designed for
(Table7.1.2). The fan coils were designed for the peak cooling loads per room. In order
to compare the fan coil unit to the VE-Pro room loads, the total sensible cooling loads of
each fan coil unit were compared with the peak maximum sensible cooling load of each
room. This proves that the model has been accurately modeled to match the actual
Lakeview Terrace Library.
The library’s total cooling load was designed for 268,300 BTUH. The model
generated a total peak cooling load of 220,976 BTUH, with a mean cooling load of
23,016 BTUH and a minimum cooling load of 2,018 BTUH. The main reading room,
where the night flushing study will take place, was designed for a total cooling load of
149,900 BTUH. The model calculated a total peak cooling load for the main reading
room (Figure 7.1.9) of 123,144 BTUH with a mean cooling load of 11,108 BTUH.

Figure 7.1.9 – Main Reading Room Cooling Loads
116

The library has now been modeled for architecture, thermal comfort, internal
heat gain, solar heat gain, and cooling loads. The next steps will be to begin simulating
the library using night flushing. Modeling the building correctly was extremely important
to ensure the integrity and accuracy of the forthcoming simulations. The yearly cooling
loads peak during the months of June to October, the cooling months. These months
will be the main dates of focus, night flushing during this time range will determine how
much natural ventilation will be needed to accurately cool the space.

7.2 – Building Simulation without Passive or Active Heating and Cooling
Before night flushing was implemented, it was important to simulate and
understand what the building’s thermal conditions were, without the aid of HVAC or
passive cooling. All of the parametric night flushing tests will start from these initial
results on interior temperature and thermal comfort. The main reading room’s interior
temperature, exterior dry bulb temperature, and the outdoor wind speed (Figure 7.2.1)
are valuable because they show the relationship between a cooler exterior, the building
envelope, and a warmer interior. In order to night flush the building, the exterior
temperature needs to be cooler than the interior and an appropriate amount of outdoor
wind needs to be ventilated into the building. The simulation of the library’s air
temperature shows that the interior temperature can peak in late September at 94°F,
be as low as 51° F on December 13
th
, and has mean interior temperature is 70.64°F.
During the cooling months of June through September the mean interior temperature is
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Figure 7.2.1 – Air Temperature, Outdoor Dry Bulb Temperature, Wind Speed
87.64°F. The dry bulb temperatures for Sylmar show that the climate peaks at 95°F, has
a low of 39°F, and a mean temperature of 62°F. The wind speed peaks in May at 50.6
mph, but has a mean speed of 8 mph throughout the majority of the year. Ideally, the
wind would peak during the summer months, so more air could be circulated into the
building at night. This may present a problem since the library’s reason for night flushing
not working was insufficient air CFM.
The thermal comfort of the building’s simulation (Figure 7.2.2) gave expected
results for the main reading room. During the summer without air conditioning, the
building would be somewhere between 80°F to 95°F with a peak of people dissatisfied
(PPD) of 88% in September, and a summer PPD average of 41%. The predicted mean
vote (PMV) for the main reading room peaks at 2.28 on the warm side of the thermal
sensation scale in September, and has a summer PMV average of 1.24 from June to
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September. The objective of the night flushing simulations in the reading room will be to
decrease the data on indoor air temperature, PPD, and PMV.

Figure 7.2.2 – LVT without Active or Passive Cooling PPD & PMV

7.3 – Night Flushing Simulation Using Current Architectural Features
The first night flushing simulation will show the performance of the library using
night flushing along with all of the buildings current architectural features. For night
flushing, the features that are important are the thermal mass, the window type and
location, the shading devices, and the lighting for internal heat gain. The current
building design and features were not designed for night flushing so the initial
simulation should have the same outcome. Unlike the actual library, this simulation will
give data that can lead to improvements.
In order to use natural ventilation, the windows have to be made operable. Since
the library was constructed with operable windows, the simulation will be modeled
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using the same operable windows. In the MacroFlo Opening Types tool of VE-Pro, the
two types of operable windows in the main reading room were applied. The ten upper
south side windows of the main reading room are 45 sq. ft. and 43% of each window is
operable and located 14 feet above the floor level. The six north side windows of the
main reading room are 75 sq. ft., and 6.5% of each window is operable and located 3
feet above the floor level. The other operable windows of the library are in the lobby
and the multi-purpose room. The four lobby windows are 35 sq. ft., and 25% are
operable and located 3 feet above floor level. The four operable windows of the multi-
purpose have the same operable window characteristics as the top south side windows
of the main reading room.
A key component in effectively night flushing a building is having the operable
windows open for the proper time frame throughout the night. For this simulation the
time range used for the windows was 7:00 PM till 6:00 AM (Figure 7.3.1). For the
majority of the year in Southern California, typically the outdoor air is much cooler by
seven o’clock in the evening and the sun typically rises around the time of six in the

Figure 7.3.1 – Operable Window Schedule
120

morning during the summer. This operable window schedule seems like an appropriate
starting point. Different window schedules will be investigated and tested in the fifth
simulation of this study.
The results of the simulation show a significant decrease in the peak interior
temperature of the main reading room that was expected due to the introduction of
cooling. The mean temperature from the months of June through September dropped
from 87.64°F to 79.4°F. With night flushing, the thermal mass needs to be cooler than
the indoor space during the day and warmer than the interior temperature (Tᵢ) at night
to be effective. When evaluating the mean radiant temperature (Figure 7.3.2), it should
have an average minimum night temperature greater than the minimum night interior
temperature. This will show that the thermal mass is absorbing the heat that was in the
space. According to the simulation, the mean radiant temperature of the thermal mass
and the interior temperature are very similar. During the day of the cooling months the
mean radiant temperature is on average 80.1°F which is hotter than the mean air

Figure 7.3.2 – Main Reading Room Tᵢ vs. MRT
121

temperature of 79.4°F. At night the mean radiant temperature is on average 73.9°F,
and the mean air temperature is 71.5°F. This is showing that the building is being
cooled by natural ventilation but not by night flushing. The thermal mass is not cooling
enough at night to absorb enough heat during the day.
In order to truly evaluate the interior temperature, the night flushing should be
designed to improve the peak annual temperature. The peak indoor temperature for
the main reading room is 84.79°F, down from 94°F on September 24
th
when the outdoor
temperature peaks at 95.0°F, and the mean radiant temperature is 83.46°F (Figure
7.3.3). The chart also shows the wind speed for the peak cooling day. The average wind

Figure 7.3.3 – Main Reading Room Peak Tᵢ and Tₒ, MRT, &Natural Ventilation

speed on September 24
th
at night when the operable windows are open is 6.1 mph,
peaking at 15.0 mph at 7:00 PM. The annual average wind speed is 8.0 mph and the
peak is 50.6 at 7:00 PM on May 18
th
. The night time natural ventilation entering the
main reading room on the peak temperature day has a total volumetric flow rate on
average of 8291cubic feet per minute (cfm), with a peak of 16494.7 cfm at 7 PM. The
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average natural ventilation flow rate for the months of June through September is
9204.6cfm, peaking on May 18
th
at 7:30 PM with 29559 cfm.
The conduction of the exterior walls determines how much heat the thermal
mass is passing through and absorbing. The thermal mass walls of the main reading
room (Figure 7.3.4) conduct an average of 44723 BTUH of heat out of the building from
9:00 AM until 7:00 PM on the peak temperature day. During the night the walls conduct
an average of 27781 BTUH. The goal of the next simulation is to decrease the amount of
heat conducted through the exterior walls. This will prove that the thermal mass is
storing the heat.

Figure 7.3.4 – Main Reading Room Thermal Mass Conduction Gain

The level of thermal comfort for the main reading room can be determined not
only by the interior temperature but also by the PMV and the PPD of the space. With
night flushing, the summertime PPD is on average 19.6% and the PMV is 0.83 (Figure
7.3.5). From reviewing the chart in Figure 7.3.6, the main reading room’s peak
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percentage of people dissatisfied is 59% with a predicted mean vote of 1.66. These
values show that the space would be overheated and uncomfortable for most people.

Figure 7.3.5 – Main Reading Room PPD vs. PMV

Figure 7.3.6 – Main Reading Room Peak PPD & PMV
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7.4 – Enhancing the Thermal Mass
In order to enhance the effect of the thermal mass, the 8” lightweight CMU
exterior and interior walls were digitally replaced with high density 12” 75% solid
concrete high strength blocks (Figure 7.4.1). The 6” slab on grade concrete floor was
replaced by a 12” slab on grade heavyweight concrete. This type of high density
concrete can use a density of 288 pounds per cubic feet (Nelco 2004). The increase in
density and thickness should allow the thermal mass to store more heat for longer
periods of time. This will allow the interior temperature to stay comfortable deeper into
the day. The concrete’s new thickness of 12” was chosen because the maximum wall
thickness for the library is 12” in the multi-purpose room. So, by just adding 4 inches to
the concretes thickness, the wall size will not surpass the thickest wall of the building.
This also prevents the increase in wall size from reducing the square footage of the
library’s interior spaces. The increase in the mass’ heat capacity can be shown by

Figure 7.4.1 – New High Density 12” Exterior Concrete Block Wall
125

comparing the mean radiant temperature versus the interior air temperature. With the
enhanced thermal mass, the interior temperature should decrease while the mean
radiant temperature increases. A series of parametric test will be performed to see if a
12” thickness is the most effective.
The enhanced thermal mass simulation data shows a decrease in the interior
temperature as well as an increase in the annual minimum mean radiant temperature
(Figure 7.4.2). This shows that the new high density concrete is storing more heat than
the original CMU thermal mass. The mean temperature from the months of June
through September dropped from 79.4°F to 76.1°F. During the day of the cooling
months the mean radiant temperature is on average 75.8°F which is slightly less than
the mean air temperature of 76.1°F, compared to a MRT of 80.1°F and a indoor air
temperature of 79.4°F from the initial simulation. At night the mean radiant

Figure 7.4.2 – Main Reading Room Enhanced Thermal Mass Tᵢ vs. MRT

126

temperature is on average 71.8°F and the mean air temperature is 70.1°F. The MRT has
decreased from 73.9°F to 71.8°F, and the indoor air temperature has decreased from
72.5°F to 70.1°F.
The peak indoor temperature for the main reading room is 77.42°F on
September 24
th
, and the mean radiant temperature is 77°Fwhen it is a dry bulb
temperature of 95.0°F outside (Figure 7.4.3). Compared to the first simulation, the
interior temperature and mean radiant temperature have a flatter curve. The peak
indoor temperature has decreased from 84.79°F to 77.42°F and the mean radiant
temperature has cooled from 83.46°F to 77.0°F. This means that the temperatures are
more consistent with fewer high temperature peaks.

Figure 7.4.3 – New Thermal Mass Peak Tᵢ, Peak Tₒ, & MRT

The thermal mass walls of this simulation conduct an average of 28154 BTUH of
heat out of the building from 7:00 AM until 9:00 PM on the peak temperature day.
During the night the walls conduct an average of 6021 BTUH of heat into of the main
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reading room. The amount of heat conducted through the walls and out of the building
during the day decreased by 16568 BTUH, from 44722 BTUH to 28154 BTUH. The
amount of heat conducted through the walls at night decreased by 21760 BTUH, from
27781 BTUH to 6021 BTUH. The increased density of the walls has increased the heat
storage capacity, thus enhancing the effect of night flushing.
The graph (Figure 7.4.4) also shows that the library is storing heat later into the
day. The conduction change from negative to positive doesn’t occur until 9:00 PM. The
increased time lag is exactly how the thermal mass should perform to allow night
flushing to be successful.

Figure 7.4.4 – New Thermal Mass Tᵢ, Tₒ, MRT, &Wall Conduction Gain

The simulation with the high density thermal mass produced an average
summertime PPD of 13% and an average PMV of 0.50. From reviewing the chart in
Figure 7.4.5, the main reading room’s peak percentage of people dissatisfied is 26% on
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August 17
th
with a predicted mean vote of 1.00.The graph also displays a higher
percentage of people dissatisfied from being cold in the winter months. This will be
solved once the operable window schedules are altered. Right now they are open from
7 PM until 6 AM year round. The PPD for the summer has decreased from an average of
19.6% to 13% and the mean PMV has decreased from .83 to 0.50. The ASHRAE standard
for an acceptable PPD is 10%, so the mean PPD is approaching this marker. The peak
PPD decreased from 59% to 26% and the peak PMV decreased from 1.66 to 1.00 (Figure
7.4.6). So by using a high density concrete and increasing the thickness of the wall, the
percentage of people dissatisfied was cut in half and the average interior temperature
dropped by three degrees.

Figure 7.4.5 – New Thermal Mass PPD vs. PMV

129

Figure 7.4.6 – Main Reading Room with Enhanced Thermal Mass Peak PPD & PMV

130

7.5 – Enhancing the Glazing
Besides the thermal mass and natural ventilation, the next major factor in
implementing night flushing is reducing the library’s solar heat gain. After reviewing the
solar studies of the library, it was determined that the shading would be left as is and
saved for a future study. With the shading techniques remaining as constructed, the
other way to reduce solar heat gain is to use a different type of glazing with a more
efficient shading coefficient. By using a type of glazing with a more effective shading
coefficient, the solar energy heat transmittance through the windows into the library
will be reduced. The current windows of the main reading room use a double pane low
e glazing with a shading coefficient of 0.42 on the lower south facing windows and a
shading coefficient of 0.89 on the upper south facing windows. These windows were
selected to allow more light into the space through the upper windows, which are
shaded with a louvered overhang. Allowing more daylight into the space will reduce the
lighting energy consumption but also increase the solar heat gain. In this simulation, a
different type of glazing will be used that has a more effective shading coefficient than
0.89 in order to reduce the solar heat gain.
Potential issues with reducing the shading coefficient are that it will result in a
decrease in visibly transmittable light; this could lead to an increase in lighting
consumption. Another issue is that the solar heat gain will not only be decreased in the
summer but it will be decreased in the winter when it is needed. To make sure that
using a glazing with a more effective shading coefficient would not greatly increase the
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lighting and heating consumption, a series of parametric tests were run that proved that
the increases in lighting and heating would be minimal, and the results of using a
different type of glazing will prove to be beneficial and not result in a large energy
increase by any other system of the building. In order to reduce the solar heat gain with
just the shading, the device would have to be increased in size which would still reduce
the daylight and lead to an increase in lighting. It would also result in more sunlight
being shaded into the winter which would increase the need for heating. A future study
would be very beneficial to how the shading devices could be altered to lead to a more
effective reduction in solar heat gain than by changing the glazing.
Using the program Windows 6, a new double pane low E glass (Figure 7.5.1) was
constructed for the library. The glazing was constructed using a two quarter inch clear
glass panels with a half inch argon filled cavity. The outer layer of glass is a clear low E
Viracon window, with a solar transmittance of .226 and the low e coating on the inside
surface of the glass. The inner layer of glass is a clear Viracon window with a solar
transmittance of .771. Windows 6 calculated the new window to have a U- value of

Figure 7.5.1 – Windows 6 – New Double Pane Low E Glazing Parameters

132

0.227, a T
vis
of 0.386, a shading coefficient of 0.278, and a solar heat gain coefficient of
0.242. The new window was then inserted into VE-Pro by entering the values and
parameters derived from Windows 6 into the VE-Pro window construction tool. After
the new window data was input into the VE-Pro model, the building was simulated with
the intent of lowering the main reading room’s interior temperature and PPD by
decreasing the value of the shading coefficient to 0.227.
The results of this simulation show (Figure 7.5.2) a decrease in the average and
peak interior temperature of the main reading room. The mean temperature from the
months of June through September dropped from 76.1°F to 75.1°F during the day. The
new glazing also resulted in a decrease in the mean annual solar heat gain from 8124
BTUH to 5226 BTUH. The new glazing of this simulation also conducts an average of
2138 BTUH of heat into the building from 7:00 AM until 9:00 PM. During the night the
windows conduct an average of 3074 BTUH of heat out of the building.

Figure 7.5.2 – Main Reading Room with New Glazing Tᵢ, SHG, &Glazing Conduction

133

The peak indoor data (Figure 7.5.3) for the main reading room shows a decrease
in interior temperature from 77.42°F to 76.76°F on September 24
th
when the outdoor
temperature peaks at 95.0°F. The peak solar heat gain decreased from 28249 BTUH in
the summer to 18122 BTUH at 12:30 PM, and the average solar gain for the peak day
decreased from 9815 BTUH to 4879 BTUH. The peak solar heat gain day for the entire
year is December 20
th
. The peak solar heat gain for that day is 42204 BTUH, which is a
21905 BTUH decrease from 64109 BTUH at 11:30 AM with an average solar gain
decrease from 16140 BTUH to 10409 BTUH. The new glazing conducts a peak of 10725
BTUH of heat into the building at 12 PM on the peak temperature day. During the night
the windows conduct a peak of 11846 BTUH of heat out of the building. By selecting
new glazing with a more effective shading coefficient, the solar heat gain and external
glazing heat conduction were reduced enough to decrease the summertime interior air
temperature of the library.

Figure 7.5.3 – Main Reading Room Peak Tᵢ and Tₒ, SHG, & Glazing Conduction
134

The simulation with the new glazing produced an average summertime PPD of
11.5% and an average PMV 0.46 (Figure 7.5.4). From reviewing the chart in Figure 7.5.5,
the main reading room’s peak percentage of people dissatisfied is 23% on August 17
th

with a predicted mean vote of 0.92. The PPD for the summer has decreased from an
average of 13% to 11.5% and the mean PMV has decreased from 0.50 to 0.46. The peak
PPD decreased from 26% to 23% and the peak PMV decreased from 1.00 to 0.92.

Figure 7.5.4 – Main Reading Room PPD vs. PMV

Figure 7.5.5 – Main Reading Room Peak PPD & PMV
135

7.6 – Altering the Operable Window Schedule

To make sure the operable windows were open for the ideal time range in order
to maximize night flushing, a series of tests were administered with the windows open
for different frames of time. In order to meet ASHRAE 55 standards for adaptive
comfort, all of the operable windows which are opened with actuators that are
connected to the EMS system will also be manually operable for the occupants as well.
The original operable window schedule was set for the windows to open at 7:00 PM and
close at 6:00 AM. The tests will simulate the building using the times frames of 8:00 PM
until 6:00 AM, 7:00 PM until 7:00 AM, 7:00 PM until 8:00 AM, 7:00 PM until 9:00 AM,
7:00 PM until 10:00 AM, and a schedule with the windows open all day. After simulating
the building with these different operable window schedules, having the windows open
from 7:00 PM until 8:00 AM gave the best results. The main reading room’s mean
summertime temperature decreased from 75.1°Fto 73.5°F, and the peak indoor

Figure 7.6.1 – Interior Temperature vs. PPD for New Operable Schedule
136

temperature on September 24
th
went from 76.76°F to 76.31°F (Figure 7.6.1).The PPD for
the summer has decreased from an average of 11.5% to 10.9% and the mean PMV has
decreased from 0.46 to 0.42. The peak PPD decreased from 23% to 21% and the peak
PMV decreased from 0.92 to 0.87. The improvements in terms of interior air
temperature, PPD, and PMV were minor but the windows being open an extra two
hours does in fact cool the interior temperature by an average of 1.6°F.
In all of the previous simulations, night flushing was run for the entire year, and
focused primarily on the results of the summer months of June through September. In
order for the simulations to be more accurate, the operable window schedule must
meet a certain set of parameters. The parameters are based on the necessary interior
and exterior climate conditions needed for night flushing. The exterior and interior
temperatures of the library without the operable windows open (Figure 7.6.2) will
determine when the windows should be open for night flushing.

Figure 7.6.2– Interior Temperature without Night Flushing vs. Exterior Temperature

137

For the operable windows and night flushing to be activated, operable window
control conditions need to be set (Figure 7.6.3). There first must be at least a 16°F
temperature difference between the outside air temperature and the desired indoor
temperature of 73°F.

Figure 7.6.3 – Operable Window Control Conditions

The night time outdoor temperature must be 68°F or less, and less than the interior
temperature and thermal mass temperature. If all of these parameters are met and the
interior temperature is going to be greater than the desired 73°F, then the operable
windows are opened and night flushing is activated. If the exterior temperature exceeds
80°F, then night flushing usually cannot be effective for the entire day.
The library does not adhere to the trend of the exterior temperature not
exceeding 80°F. The high density thermal mass allows the library to night flush even
when the outdoor temperature is over 90°F. On September 24
th
the exterior
temperature peaks at 95°F at 12 PM and is over 90°F for 5 hours. When the windows are
closed and night flushing is not being used, the space can reach a peak of 84.69°F and an
average of 82.1°F during the day. When night flushing is activated, the interior
138

temperature is steadily between 70.29°F to 76.31°F during the day with a peak PPD of
12 at 5:30 PM and an average PPD of 10.9 (Figure 7.6.4).

Figure 7.6.4 – Peak Interior Temperature with Night Flushing vs. Without

The new operable window schedule with the windows open from 7:00 PM until
8:00 Am and the new operable control conditions result in the windows being open
around May28th until around October 6
th
(Figure 7.6.5). The windows are only open
during the days that meet the night flushing parameters in this time frame, but they
seem to be open for the majority of the days of those months.

Figure 7.6.5 – Tᵢ with Night Flushing Schedule vs. Tₒ
139

7.7 – Enhancing the Lighting System

The objective of enhancing the lighting system of the library it to reduce the
internal heat gains as well as the total lighting energy consumption. The main reading
room uses incandescent ambient lighting throughout the space. If the space used
fluorescent lighting then the building could receive the same amount of lumens of light
for approximately one third of the energy and sensible heat gain. This will bring the
same amount desired light into the space and it will still reduce the energy consumption
of the building from power and heat generated by the lighting. The lighting will also
have continuous dimming built into the system to control lighting levels in unison with
the daylighting of the building. Other than the overall energy conservation of using
fluorescents over incandescents, the main objective of this study is to maximize the use
of night flushing by reducing the internal heat gain.
The spaces of the library that use incandescent lights are the main reading room,
the lobby, the main bookstacks, and the multi-purpose room. All of the incandescent
lights of these spaces were replaced with fluorescent ambient lights. The main reading
room went from using an incandescent that produced 3.01 W/ft² to a fluorescent that
produces a maximum sensible gain of 0.8 W/ft². The lobby went from using an
incandescent of 1.91 W/ft² to a fluorescent that produces 0.7 W/ft². The main
bookstacks went from 1.7 W/ft² to 0.77W/ft². The multi-purpose room went from
2.25W/ft² to 0.75 W/ft². Knowing the maximum sensible gain of the lighting in the
lobby, main bookstacks, and multi-purpose room are important for generating the
140

buildings total energy consumption after all of the night flushing simulations have been
completed. The main reading room’s lighting gain decreased from 43254 BTUH to 14148
BTUH which is about 21.0% of the total internal heat gain of 68421 BTUH behind the
occupants and the high total of computers in the main reading room (Figure 7.7.1).

Figure 7.7.1 – Internal Gains

Despite the large decrease in the internal heat gain from light, the overall
temperature only had a slight decrease due to the large volume of the main reading
room. The main reading room’s mean summertime temperature (Figure 7.7.2) during

Figure 7.7.2 – Interior Air Temperature with Enhanced Lighting
141

the day decreased from 73.5°F to 73.04°F, and the peak indoor temperature on
September 24
th
went from 76.31°F to 75.55°F. This puts the building right around an
average temperature of 75°F, which is the main reading room’s desired temperature.
The PPD for the summer has decreased from an average of 10.9% to 9.5% and
the mean PMV has decreased from 0.42 to 0.39. The peak PPD decreased from 21% to
18.5% and the peak PMV decreased from 0.9 to 0.81.
The lighting enhancement’s main contribution to the building is on the total
lighting energy consumption (Figure 7.7.3). By changing the lighting to fluorescents in
the main reading room, lobby, main bookstacks, and multi-purpose room, the library’s
total lighting energy consumption decreased from 57.861 KBTUH to 26.472 KBTUH. The
energy utilized on lighting was decreased by 45% without sacrificing the amount of light
produced, and at the same time reducing the interior temperature of the building.

Figure7.7.3 – Light Energy Consumption

142

7.8 – Cooling the Rest of the Library

The initial thought on night flushing in the Lakeview Terrace Library was that it
would only be successful in the main reading room. After performing all of the tests to
enhance the performance of night flushing, the simulations show that night flushing is
successful in the main reading room, the main bookstacks, the multi-purpose room, the
main restroom, and the lobby. The main reading room and the rest of the spaces of the
library need a mechanical system in case the night flushing breaks down. There are also
spaces which natural cooling is improbable and mechanical cooling is necessary. The
next step is for the HVAC system to be implemented into the simulation, so the
building’s total energy can be calculated.
The lobby simulation shows that night flushing is effective from July through
September, the lobby has an average daytime interior temperature of 71.39°F and a
peak interior temperature of 73.72°F on September 25
th
(Figure 7.8.1). The lobby’s
average summer PPD is 6% with an average PMV of 0.16, and it has a peak PPD of
13%on August 16
th
with a peak PMV of 0.63 (Figure 7.8.2).

Figure 7.8.1 – Lobby Night Flushing Interior Temperature
143

Figure 7.8.2 – Lobby Night Flushing PPD and PMV

The main restroom simulation shows that night flushing is effective during the
months of July through September, the main restroom has an average daytime interior
temperature of 70.34°F and a peak interior temperature of 72.48°F on August 17
th

(Figure 7.8.3). The lobby’s average summer PPD is 6% with an average PMV of 0.12, and
it has a peak PPD of 10% with a peak PMV of 0.49.

Figure 7.8.3 –Main Restroom Tᵢ, PPD, & PMV
144

The main bookstacks are openly connected to the main reading room, so the
night time air ventilated from the main reading room’s windows cools the thermal mass
of the main bookstacks as well. The simulation shows that night flushing is effective
during the months of July through September, the lobby has an average daytime interior
temperature of 70.7°F and a peak interior temperature of 76.46°F on September 25
th

(Figure 7.8.4). The lobby’s average summer PPD is 7% with an average PMV of 0.24, and
it has a peak PPD of 20% with a peak PMV of 0.85.
.
Figure 7.8.4 –Main Bookstacks Tᵢ, PPD, & PMV

Night flushing was able to work in the multi-purpose room, but mechanical
cooling was needed for certain times of the year. The interior temperature surpasses
78°F on days from August through September. It has four operable windows and a large
volume of 18480 cubic feet which makes it difficult to cool for the entire day. Using
night flushing from June through September, the space has an average daytime interior
temperature of 74.8°F and a peak interior temperature of 79.3°F on August 17
th
(Figure
145

7.8.5). The lobby’s average summer PPD is 12% with an average PMV of 0.47, and it has
a peak PPD of 41% with a peak PMV of 1.32 (Figure 7.8.6).

Figure 7.8.5 –Multi-purpose Room Interior Air Temperature

Figure 7.8.6 –Multi-purpose Room Interior Air Temperature

The last zone of the library is the staff work workroom. The staff workroom is
walled off from the main bookstacks and is surrounded by the staff lounge, a staff office,
the I.T. room, the mechanical and electrical rooms, and the custodial closet. The staff
lounge and office have operable windows but not enough to cool all of the spaces, so
mechanical cooling will be used to keep these spaces comfortable.
146

The use of natural and mechanical ventilation makes the Lakeview Terrace
Library a mixed mode building. It uses natural and mechanical ventilation for cooling the
same space but at different times which makes it a change-over system. The heating
and cooling systems for the simulation use the same nine fan coil system that the library
is currently using. Heating the library consumes the majority of the HVAC energy, with
night flushing generating a minimal cooling load. The system still needs to be designed
for the interior loads though. Even though night flushing is cooling the majority of the
spaces, the HVAC system needs to be implemented for the zones in which night flushing
does not work, for extreme days, and to be used as a backup system in the event night
flushing is not working or the operable windows malfunction, which is one of the
problems with the current building. The cooling and heating profiles are set for an hour
before and after for the library’s occupancy time range from 8:00 AM until 10:00 PM.
Since the interior loads of the library have changed, the heating and cooling
loads of the library needed to be recalculated (Table7.8.1). The changing of the lighting
from incandescent to fluorescent reduced the internal heat gain, and the new window
glazing reduced the solar heat gain. The new room loads resulted in the resizing of the
boiler and the chiller. The boiler was resized to be designed for the peak load of 375.5
KBTUH from 328.6 KBTUH. The increase in heating is due to the reduction in lighting and
solar heat gain. The chiller was resized to the peak load of 167 KBTUH from 268.3
KBTUH. The reduction in the chiller load outweighs the increase in the boiler load.
147

Room FCU
New Peak
Sensible
Cooling
Load (BTUH)
New FCU -
Sensible
Cooling
Load
(BTUH)
New
Total
Cooling
Load
New
Total
FCU
Cooling
Load
New
Peak
Sensible
Heating
Load
(BTUH)
New FCU
- Sensible
Heating
Load
(BTUH)
New
Total
Cooling
Load
New
Total
FCU
Cooling
Load
Main Reading Room Zone 1 1 20343 21000
89371 90000
50531 51000
234186 235500
Main Reading Room Zone 2 2 18448 18500 46951 47000
Main Reading Room Zone 3 3 18340 18500 47428 47500
Main Reading Room Zone 4 4 17912 18000 46777 47000
Main Reading Room Zone 5 5 14328 15000 42499 43000
Main Bookstacks 6 13762 -
15602 16000
37804 -
40511 41000
Mech. Room 6 882 - 1626 -
Electrical Room 6 958 - 1081 -
Staff Workroom 7 6275 -
15430 16000
14607 -
30351 30500
Staff Lounge 7 3557 - 5177 -
Staff Storage 7 343 - 3228 -
Staff Restroom 7 798 - 2953 -
Head Librarian's Office 7 2142 - 2782 -
I.T. Room 7 2072 - 0 -
Custodial Office 7 243 - 1604 -
Multi-Purpose Room 8 30176 45000
44259 45000
23279 23500 23279 23500
Evaporative Cooling Tower 9 2965 No Cooling 4971 -
44751 45000
Lobby/Entrance 9 7713 No Cooling 19284 -
Lobby Storage 9 238 No Cooling 2894 -
Main Restrooms 9 3167 No Cooling 17602 -
TOTAL - - - 164662 167000 - - 373078 375500
Table 7.8.1 – New Cooling and Heating Loads

Using the new heating and cooling loads, the HVAC system was designed in VE-
Pro’s ApacheHVAC tool (Figure 7.8.7). The temperature set points are 68°F for heating
and 75°F for cooling. The system also sets up an outside air supply for each zone at 0.15
cfm/ft², this allows the removal of stale air during the summer days when the HVAC
system is off. It also allows fresh air to be introduced into the space for acceptable
indoor air quality. The library also takes into account air infiltration and air exhaust. The
libraries air infiltration rate is 0.5 air changes per hour. The exhaust fans are located in
148

the main restroom, staff restroom, custodial office, mechanical room, and electrical
room . The main restroom’s fan moves air out at 900 cfm, the staff restroom fan moves
200 cfm, the custodial closet moves 100 cfm, and the mechanical and electrical room
exhaust a combined 900 cfm.

Figure 7.8.7 – VE-Pro Fan Coil System

The fan coil units are sized for the internal heat gains, but because the building is
night flushed the actual cooling loads peak at 24.4 KBTUH on September 24
th
while the
heating load peaks at 371.04 KBTUH on December 13
th
(Figure 7.8.8). The average
heating load for the winter is 45.776 KBTUH and the average mechanical cooling load for
the building is 3.9 KBTUH. The effect of night flushing can already be seen in the
reduction in the cooling load.

Figure 7.8.8 – Heating & Cooling Load with New HVAC & Night Flushing
149

Now that the HVAC system has been incorporated along with the natural
ventilation system of night flushing, the library’s interior temperature during the day is
thermally comfortable year round (Figure 7.8.9). Night flushing will keep the building
cool during the summer for far less energy than the current building system and the
HVAC system will keep the building comfortable during the winter. The large decrease in
the buildings cooling load due to the implementation of night flushing, and the ability of
night flushing to greatly reduce the library’s cooling will show a huge decrease in the
library’s total energy consumption.

Figure 7.8.9 – Tᵢ with New HVAC & Night Flushing

7.9 – Energy Consumption

The VE-Pro simulations of the Lakeview Terrace Library with the natural
ventilation technique of night flushing produced an annual building energy consumption
of 416.5 MBTU’s. The program generates an energy report through the IES ApacheSim
module which conforms to ANSI/ASHRAE Standard 140. The report breaks down the
library’s total energy consumption per month for heating, cooling, fans – pumps –
150

controls, lighting, and equipment (Table 7.9.1). The total heating energy consumption is
161.8 MBTU’s, cooling consumes 5.3 MBTU’s, fans – pumps – controls consumes 89.8
MBTU’s, lighting consumes 56.6 MBTU’s, and equipment consumes 103.0 MBTU’s. The
peak heating month is January which consumes 35.3 MBTU’s of energy in comparison to
the peak cooling month of August which consumes 1.2 MBTU’s of energy. From
comparing the heating and cooling energy consumption, the impact of natural
ventilation on the library is significant.

Table 7.9.1 – Monthly Energy Summary

The original Energy-Pro energy model and the 2008 Lakeview Terrace Library
energy bill both give their energy totals in kilowatt hours for site energy, so the VE-Pro
energy results were converted from MBTU’s to kWh’s and do not account for the total
source energy. If the total source energy was calculated for this study, the total
electrical energy would be about 3 times greater to account for the energy needed to
generate and transport the electricity. The conversion factor is 1 kWh equals 3412 BTU
and 1 BTU equals 1000000 MBTU, so 1kWh equals 3412000000 MBTU. The total annual
site energy consumption of the library converts from 416.5 MBTU’s to approximately
151

121,833 kWh. The converted annual site energy consumption per energy source in
kilowatt-hours are 47,418 kWh’s for heating, 1,553 kWh’s for cooling, 26,318 kWh’s for
fans, pumps and controls, 16,588 kWh’s for lighting energy, and 30,186 kWh’s for the
building’s equipment and computers (Figure 7.9.1).

Figure 7.9.1 – Energy Consumption Breakdown

The library’s energy consumption can be broken into two categories: natural gas
and electricity. The average natural gas consumption for the year is 18.519 kBTUH with
a peak of 453.77 kBTUH on December 13
th
. The average annual electrical consumption is
29.16 kBTUH with a peak of 86.1 kBTUH on September 25
th
(Figure 7.9.2).

Figure 7.9.2 – Total Natural Gas vs. Total Electricity
152

The simulated energy results of the library generated a total annual electrical
energy consumption of 74,645 kWh and an annual gas energy consumption of 47,418
kWh, giving the library an annual energy consumption of 122,063 kWh. In order to
calculate the actual total energy consumption, the energy generated from the
photovoltaic cells on the roof and the entrance trellis need to be deducted from the
annual energy consumption. The calculated PV energy consumption for the library is
19,087 kWh for the year. Factoring the electrical energy, natural gas energy, and the
energy generated from the PV system, the Lakeview Terrace Library with night flushing
was simulated as having a total energy consumption of 102,796 kWh (Table 7.9.2). The
library’s current cost per kilowatt-hour from the Los Angeles Department of Water and
Power (LADWP) is $0.12/kWh. Applying this rate to the total energy consumption, the
simulated annual energy consumption for the naturally ventilated library would be
$12,335.52.
Electricity Energy 74,645 kWh
Gas Energy 47,418kWh
Energy Consumption 122,063 kWh
PV Energy Generated -(19,087) kWh
Total Energy Consumption 102,976 kWh
Cost per kWh $0.12/kWh
Energy Bill $12,357.12
Table 7.9.2– LVT Night Flushing Simulation Energy Totals

Along with the total energy consumption, the simulation produced the library’s
carbon footprint (Table7.9.3). The energy modeled generated total carbon dioxide
emissions of 89,726.1 lbCO2.The heating and cooling system’s CO2 emissions is 46,213.3
153

lbCO2, peaking in January with a total of 6,425.5 lbCO2. The lighting system annually
emits 15,434.2 lbCO2 and the building equipment emits 28,078.6 lbCO2. On an hourly
basis (Figure 7.9.3), the library emits an average of 39.4 lbCO2/hr during the occupied
hours of the winter, peaking at 81.7 on December 13
th
. During the summer the library
emits an average of 21.1 lbCO2/hr, peaking at 55.6 on June 14
th
.

Table 7.9.3 – Monthly Carbon Emissions

Figure 7.9.3 – Total System Carbon Emissions

154

Chapter 8: Lakeview Terrace Library Night Flushing and Energy Analysis
8.1 – Night Flushing Analysis
The results of the night flushing simulations show that the interior temperatures
and percentage of people dissatisfied meet acceptable levels for thermal comfort. In
order for the library to be naturally conditioned it also had to meet a series of natural
ventilation requirements, which it did meet. The library’s envelope allows less than 4
w/sq ft of sensible solar gain. The internal heat loads are 2 w/sq ft and below. For at
least 30% of the occupied hours the monthly mean maximum temperature for the
climate zone is less than 80°F, the mean minimum temperature is greater than 32°F, and
there is less that 70% relative humidity. The library is built in a park in Sylmar, so the air
quality meets the ASHRAE 62.1 Standards. The window area is at least 5% of the floor
area and the size of the main reading room allows for 20 ft. access from either side of
the space. The psychrometric chart from Chapter 5 shows that the climate data has few
days in which the outdoor temperature is greater than 80°F and night temperatures are
consistently 68°F or less for 8 hours of the night. The fact the library’s interior and
exterior climates meet these requirements is why night flushing was proven to be
effective.
The cumulative parametric tests performed on the thermal mass, glazing,
lighting, operable windows, and mechanical system proved that night flushing can be
effective in the library. The results produced by the night flushing simulations show that
the main reading room meets the Thermal Comfort – ISO 7730 standard of the PPD
155

being less than 20% for a naturally ventilated space (Table 8.1). The main reading
room’s peak interior temperature using natural cooling is 75.6°F with a Peak PPD of
14.0. The methods for analyzing the simulation’s thermal comfort data are an air flow
movement model to visually see the interior airflow variances of the library and
inputting the library’s interior temperature data into the adaptive thermal comfort
chart.

Table 8.1 – Occupied Hours Environmental Comfort

8.1.1 – Air Flow Analysis
The cool night time airflow that enters the library throughout the night travels
from the upper south side windows through main reading room and back to the exterior
through the north side windows. The air moves through the building at night as it was
expected to move through the building during the day. The shape and curve of the roof
aid in funneling the wind from the higher elevation of the south to the lower elevation
156

of the operable windows of the north side. The building was designed to funnel daytime
air through the main reading room with the thermal mass absorbing heat from the air,
creating a cool breeze that would be sent through the main reading room and into the
hot courtyard. Night flushing the library uses the same type of theory. During the night
as the cool air moves from the south windows down through the north windows, the air
absorbs the daytime heat that is stored in the thermal mass and then removes that heat
as the warmed air is ventilated out of the building (Figure 8.1.1).

Figure 8.1.1 – Main Reading Room Air Flow Diagram

The average climate day for the Lakeview Terrace Library is August 17
th
when it
is 66°F throughout the night and an average of 74.25°F in the day time, with a peak of
77°F. During the night time on August 17
th
the average wind speed is 9.8 mph with an
average wind direction of 241.3° east of north. According to the simulation (Figure
8.1.2) the average volumetric flow of night time natural ventilation through the main
reading room is 6933 cfm (4.2 ach), which is right around the acceptable range of 2-4
157

ach. Air change per hour is calculated by multiplying the CFM by 60 minutes / 1 hour
then dividing the cubic feet per hour by the total volume of the space. The ventilation of
heat absorbed from the thermal mass into the cool air is on average 11387 BTUH and
peaks at 47750 BTUH when the operable windows open at 7:00 PM. The large peak of
heat removed from ventilation is due to the removal of the warmer air that has
accumulated in the main reading room throughout the entire day as well as the heat
being absorbed from the thermal mass.

Figure 8.1.2 – Main Reading Room Volumetric Flow

The night time air flow can be broken down by cubic feet per minute of entering
airflow per operable window for the peak climate day of August 17
th
. The south wall of
the main reading room has 10 operable windows at a 20 foot elevation (Figure 8.1.3).
They are each 20 square feet. The cfm of airflow on the windward side entering each
window starting from the west is 1130, 1248, 1248, 1057, 1057, 1000, 1000, 939, 939,
158

and 899, totaling 10517 cfm. 10517 cfm converts to approximately 6.4 air changes per
hour (ach). The typical natural ventilation ach during occupied hours is 2 – 4 ach and 6

Figure 8.1.3 – Night Flushing Interior Air Flow

ach for mechanical systems. So a peak of 6.4 ach during unoccupied hours is perfectly
acceptable especially since more air needs to be introduced into the space to provide
cooling for the next day.
The north wall, leeward side, of the main reading room has 7 operable windows
at a 3 foot elevation (Figure 8.1.4). They are each 6 square feet. The cfm of airflow
leaving through each window starting from the west is 941, 941, 947, 939, 937, 937, and
1393. A small amount of air flow is also circulated back through the south wall windows,
from which the air was supplied, to the exterior. The cfm of airflow out of these
windows starting from the west is 235, 526, 282, 282, 321, 321, 362, 362, and 390,
producing a total outflow of 10116 cfm. The rest of the airflow is supplied to the main
bookstacks and the lobby.
159

Figure 8.1.4 – Night Flushing Exterior Air Flow

The thought that insufficient airflow is the reason why night flushing the building
was the not working is incorrect. The airflow and wind movement is sufficient; the
problem was the density thermal mass did not have a high enough heat storage capacity
to work with the cool night time air. The air velocity and its movement through the
building show that the natural ventilation is properly flowing through the library at night
from entering the south side windows and leaving through the north side windows and
transferring the heat from the air and thermal mass with it.

8.1.2 – Adaptive Comfort Chart
The ASHRAE 55 adaptive comfort chart determines the acceptable thermal
comfort range in a naturally ventilated building. It graphs the dry resultant temperature
of the peak temperature day for a month with the mean monthly outdoor temperature
for that month. The dry resultant temperature is the average of the indoor air
temperature and the mean radiant temperature (Simmonds 2001). The dry resultant
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and mean monthly outdoor temperatures that were generated from the simulations
were inserted into the adaptive comfort chart for the cooling months of June through
September when night flushing is used. For the month of June (Figure 8.1.5), the mean
monthly outdoor temperature is 63.76°F, the maximum dry

Figure 8.1.5 – June Adaptive Comfort Chart

resultant temperature day was June 30
th
, the maximum dry resultant temperature was
72.52°F and the minimum dry resultant temperature for that day was 66.46°F. The chart
shows that all of the day time temperatures are within the thermal comfort range. The
temperatures that are below the range are the acceptable night time temperatures,
which is perfectly fine since the building is unoccupied at night. The night time
temperatures are not critical in analyzing the thermal comfort of the occupied hours
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especially in Southern California where night temperatures usually are at the bottom of
the temperature range.
For the month of July (Figure 8.1.6), the mean monthly outdoor temperature is
67.6°F, the maximum dry resultant temperature day was June 29
th
, the maximum dry
resultant

.
Figure 8.1.6 – July Adaptive Comfort Chart

temperature was 74.66°F and the minimum dry resultant temperature for that day was
70.36°F. The chart shows that all of the day time temperatures are within the thermal
comfort range. The minimum night time temperature seems high, but for night flushing
the cool night time sub-68°F air is absorbing the heat from the thermal mass. The
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entering outside air is on average 67.08°F and as it absorbs the heat of the mass and the
room, it increases to an average of 70.36°F
For the month of August (Figure 8.1.7), the mean monthly outdoor temperature
is 68.2°F, the maximum dry resultant temperature day was August 17
th
, the maximum
dry resultant temperature was 75.1°F and the minimum dry resultant temperature was
70.23°F.The day time temperatures for the August 17
th
are all within the thermal
comfort range.

Figure 8.1.7 – August Adaptive Comfort Chart

For the month of September (Figure 8.1.8), the mean monthly outdoor
temperature was 67.9°F, the maximum dry resultant temperature day was September
25
th
, the maximum dry resultant temperature was 75.21°F and the minimum dry
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resultant temperature for that day was 69.39°F. The chart shows that the day time
temperatures for the peak day of September 25
th
are all within the thermal comfort
range.

Figure 8.1.8 – September Adaptive Comfort Chart

The results of the adaptive thermal comfort charts show that night flushing in
the library during the cooling months of July through September is effective. All of the
tests prove that the daytime dry resultant temperatures are within the range of
acceptable thermal comfort for natural ventilation. The library can be naturally cooled
throughout the summer without the need for mechanical cooling. The peak indoor
temperature for this time frame is 75.73°F.

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8.2 – Energy Comparison
The energy comparison between the EnergyPro design simulation, the current
building performance, and the night flushing simulation shows the success that night
flushing has on the library’s energy consumption (Figure 8.2.1). The night flushing
simulation produced a 42% margin of decrease in total annual energy consumption from
the building’s current energy consumption of 175,122 kWh down to 102,976 kWh, and a
16% decrease from the EnergyPro design energy consumption of 121,698 kWh. The
reason for the much smaller percentage of decrease from the EnergyPro simulation and
the night flushing simulation is because of unusual variances in the EnergyPro model in
terms of internal gains, heating and cooling set-points, and EnergyPro’s overall heating
results. The electrical energy consumption of the simulation produced a 47% decrease
from the current building electrical consumption of 144,545 kWh down to 74,645 kWh,
and a reduction from the EnergyPro model of 43% down from 130,706 kWh. The large
reduction in electrical energy is due to the decrease in the use of mechanical cooling.
The natural gas reduction is minimal between the current building performance and the
night flushing simulation. The reduction is only 5% which makes sense since all of the
energy consumption strategies were aimed for natural cooling not heating. The
building’s actual total energy before the energy conservation from the photovoltaic cells
are taken into account shows a greater reduction in energy conservation between the
night flushing simulation and the current building performance. The night flushing
simulation produced a 48% margin of decrease in total annual energy consumption from
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the building’s current energy consumption of 194,209 kWh down to 121,698 kWh. The
night flushing simulation also produced a 13% decrease from the EnergyPro design
energy consumption of 140,785 kWh.

Figure 8.2.1 – Energy Comparison

To get an even more in-depth comparative analysis of the energy consumption
of the EnergyPro model, the current building consumption, and the night flushing
simulation, the total energy breakdown by system is taken into account (Figure 8.2.2).
The annual cooling energy total for the night flushing simulation produced an 86%
margin of decrease in total annual energy consumption from the building’s current
energy consumption of 37,265 kWh down to 1,553 kWh, and an 84% decrease from the
EnergyPro design energy consumption of 24,817 kWh. Since natural ventilation is used
throughout the summer, this large decrease seems drastic but it is logical. The
difference between the cooling totals between the EnergyPro model and the current
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building performance has to do with inaccuracies in the EnergyPro model. The
EnergyPro model produced by GreenWorks did not account for the interior loads of the
computers in the main reading room. The room contains 15 to 20 computers, each
generating 1.25 w/sq ft of maximum sensible heat gain. The multi-purpose room also
contains a kitchen which has heating loads that are not accounted for in the EnergyPro
model. The last factor is that the cooling set-point is set at 78°F. The cooling set-point of
78°F is a high setting, if a PPD graph was shown for this model it would have been far
above 10% for the summer.
The annual fans, pumps, and controls energy totals for the night flushing
simulation produced a 75% margin of decrease in total annual energy consumption from
the building’s current energy consumption of 99,365 kWh down to 26,318 kWh, and a
53% decrease from the EnergyPro design energy consumption of 55,113 kWh. The large
reduction in energy is due to the fact that natural ventilation is being used in place of
mechanical systems for 4 months.
The annual lighting energy total for the night flushing simulation produced a 40%
margin of decrease in total annual energy consumption from the building’s current
energy consumption and EnergyPro model of 27,395 kWh down to 16,588 kWh. This
decrease takes into account changing the incandescent lights to more energy efficient
fluorescents. The decrease in daylighting due to the effectiveness of shading coefficient
of the new glazing resulted in a slight increase in the amount of lumens needed per day.
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This is somewhat countered by the use of dimming, which controls the necessary
lighting in relation to the amount of daylighting entering the library.
The equipment of the night flushing simulation has the same total energy as the
current building performance of 30,186 kWh. The computers and other mechanical
equipment were not altered in the night flushing simulation. The difference in the
EnergyPro model total equipment energy is due directly to the computers and kitchen
not being modeled. The breakdown shows where night flushing really impacted the
building as a whole, not just in cooling but in all of the building’s systems.

Figure 8.2.2 – Energy Breakdown Comparison

The energy analysis of the library shows a significant decrease from the current
building performance to the night flushing simulation. The EnergyPro design model is
significantly less than the actual building performance. The reasons why have been
documented. The reason to compare an inaccurate model is to show how using an
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EnergyPro model for LEED certification can be extremely misleading. The EnergyPro
simulation was designed to model the building’s energy performance, but its total
energy performance is 53,424 kWh less than the actual building. The EnergyPro model
actually has a closer total energy to the night flushing simulation than the current
building which uses mechanical systems year round like the EnergyPro model was
designed. The EnergyPro model was not built for the design phase; it was built to meet a
percentage margin needed to meet Title 24 requirements and LEED certification
standards. Key information is left out and then the building is misrepresented, and then
buildings like the Lakeview Library achieve LEED Platinum Certification even though it
consumes 53,424 kWh more than it was modeled for. The following section will give a
cost analysis of the EnergyPro model, current building energy bill, and night flushing
simulation. The difference in the current bill to the night flushing simulation is the most
beneficial and important data.

8.3 – Cost Analysis
The library’s current energy bills come from the LADWP at a rate of $0.12 / kWh.
The night flushing simulation’s annual total energy consumption is 102,976 kWh which
totals to an annual cost of $12,357.12.The current building performance has a total
energy bill of $20,208.11 for 175,122 kWh. The simulation shows a 40% decrease in
total energy cost from the current building performance, the library could be saving
$7,851.00 a year (Figure 8.3.1).
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Figure 8.3.1 – Annual Cost Comparison

In order to achieve the 40% decrease in annual total energy consumption, the
library would have had to have paid a higher initial cost for each architectural feature
that was enhanced in the night flushing simulation (Figure 8.3.2). The thermal mass
walls that are currently in place are 19, 254 sf. Their original material and construction
cost was $250,000.00. The price to have originally installed the 12” high density
concrete masonry blocks would have been $328,980.49 at $17.08 per square foot. The
totals for the initial prices were generated using the RSMeans 2008 Building
Construction Data. The original construction and material cost for the 10,049.02 square
foot 6” slab on grade concrete was $65,000.00. The cost for the 12” high density slab on
grade concrete would have been $91,397.06, an increase of $26,397.06. The library’s
current glazing cost $153,167.50, and the new glazing with a shading coefficient of 0.27
would have cost $190,412.60 for 3,163 sf. of glazing area. The lighting cost $20,072.60
for materials and installation. The original lighting has a total wattage of 13,865 watts,
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about half of the lights are incandescent and the other half are fluorescent. To replace
all of the incandescents with fluorescents it would cost $5,761.25 for materials and
installation. The total cost of original equipment and construction of the night flushing
features is $636,624.35, and the total cost of the original and current building features is
$488,240.10
The additional cost to have incorporated these architectural features before
construction would have been $148,384.25, the majority of the cost is from the high
density concrete for the thermal mass walls (Figure 8.3.2). The library is currently paying
$7,851.00 dollars more a year by not using night flushing. If the building continued to
pay that additional sum every year to pay for the night flushing costs, it would be an18.9
year payback period.

Figure 8.3.2 – Annual Cost Comparison of Equipment and Construction

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Since the library is a new city building it has the ability to last well beyond 19 years. If
this were a residence, a 19 year payback would be a difficult sell due to the uncertainty
of how long a resident will live in that home. If the library would have been designed for
night flushing in the way this study’s simulations show, the payback period would have
been a legitimate possibility. The Lakeview Terrace Library could have been one of the
few LEED Platinum building’s that successfully utilized night flushing, instead of a LEED
Platinum building with non-functioning operable windows for natural ventilation and an
insufficient evaporative cooling tower.

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Chapter 9: Conclusions
9.1 –Lakeview Terrace Library Assessment
The objective of incorporating night flushing into the Lakeview Terrace Library
was to show that night flushing could have worked in the building had it been designed
correctly. The idea that night flushing was ineffective because of insufficient airflow is
an erroneous conclusion. Effective night flushing needs to be fully understood and
incorporated from the beginning of the design phase. The library is promoted in
Architecture Week as being a night flushed building: “The Library's energy performance
is over 40% more efficient than California standards. The building shell is high-mass
concrete masonry units (CMU) with exterior insulation to allow night ventilation.
Approximately 80% of the building is naturally ventilated with mechanically interlocked
windows controlled by the building's energy management system (AIA 2004).” This
thesis has proved that this in fact is not true. The library does not night flush, and
currently does not utilize any type of natural ventilation. The hypothesis for this
investigation was that by implementing night flushing, the Lakeview Terrace Library
could reduce its total annual energy consumption in half without jeopardizing the
buildings overall thermal comfort. The results of the night flushing simulations showed
that this was very close to being true. With night flushing, the Lakeview Terrace Library
was simulated to have a reduction in energy consumption of 41% with a mean
percentage of people dissatisfied of 9.5%, a mean predicted mean vote of 0.39, and all
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four summer months within the acceptability range of the adaptive thermal comfort
chart.

9.2 – Evaluation of Night Flushing on the Library’s Thermal Comfort
Through research done on the library it became clear that the library was never
actually designed for night flushing, the operable windows main purpose was to provide
natural ventilation during the day and to funnel the wind through the building to cool
the exterior courtyard. So the theory of night flushing seems like it was never fully
understood. Night flushing was attempted when the library opened because it had
exposed thermal mass and operable windows, but it was ineffective for what has been
decided as an insufficient airflow Furthermore, no documentation exists for night
flushing calculations or simulations for the library. The fact that night flushing failed is
not surprising.
The objective of the study and simulation of the library was to naturally
condition the main reading room and achieve a level of thermal comfort similar to that
of a mechanical system. The parametric tests performed on the thermal mass, glazing,
lighting, operable windows, and mechanical system proved that the main reading room
could be naturally conditioned for thermal comfort throughout the summer with a 90%
decrease in mechanical cooling energy consumption. The tests also proved that the
main bookstacks and lobby could also be cooled almost exclusively by using night
flushing with the cooling set-point at 75°F. The multi-purpose room needs mechanical
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cooling typically from 1:30 PM until 5:30 PM and the staff work zone needs mechanical
cooling from 11:00 AM until 6:60 PM, making the library a mixed mode change-over
building.
The final results of the night flushing simulation of the main reading room
demonstrate that night flushing can be successful from June through September by
cumulatively enhancing the specific architectural features of this study. The parametric
test’s intentions were to increase the heat capacity of the thermal mass, to reduce the
internal and solar loads of the building in order to decrease the cooling load, to use
passive as well as more energy efficient active systems, and to create a thermally
acceptable space while reducing energy consumption.
The thermal mass conducted on average from June through September 16862
BTUH of heat out of the building, peaking at 42117 BTUH on September 25
th
. The
exposed slab on grade concrete conducted on average during the summer 6315 BTUH of
heat out of the building, peaking at 38279 BTUH on June 2
nd
. The conduction of heat
through the wall to the exterior with the high density concrete had a significant
decrease, which showed the increase in the mass’ heat absorption. The wall also
conducted heat out of the space later in the day in combination with the mean radiant
temperature and the night time air flow. The night time airflow had an average
volumetric flow of 8207.4 cfm at night during the summer, peaking at 18824.6 cfm on
September 10
th
.
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The solar heat gain was reduced by changing out the windows for a more
efficient glazing with a shading coefficient of 0.27 instead of 0.44 which is currently
being used. The average solar heat gain for the summer months is 10452 BTUH with a
peak of 18122 BTUH on July 8
th
. The glazing conduction into the library is a summer
average of 1862.7 BTUH with a peak of 10971 BTUH on September 24
th
. The new glazing
led to a decrease in solar heat gain which in unison reduced the cooling load.
In reducing the internal loads, the results of switching from incandescent lights
to fluorescent lights reduced the internal load and energy consumption considerably.
The final results produced a total lighting sensible heat gain of 5818 BTUH during the
day, and a total internal heat gain of 46509 BTUH.
The results of these architectural enhancements for the benefit of effective night
flushing for the main reading room, the main bookstacks, and the lobby led to a reduced
need for mechanical cooling. The new fan coil loads for the entire library, mainly in the
multi-purpose room and the staff work zone, also added to the significant decrease in
the total cooling load which for the entire library is on average 6444 BUTH and a peak of
243978 BTUH on September 24
th
.
The end result of these simulations and architectural enhancements is a
thermally comfortable library that uses natural conditioning and minimal mechanical
cooling. The final results of the night flushing simulation of the main reading room are
an average summer interior temperature of 73.04°F and a peak interior temperature of
75.55°F on September 24
th
. The final thermal comfort results are an average PPD of
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9.5% and a peak of 18.5% on September 24
th
(Figure 9.2.1). The average PMV is 0.39
and the peak is 0.81 on September 24
th
. These results combined with the adaptive
thermal comfort charts for all of the summer months and the library has met the
desired thermal comfort target values. What this proves is that night flushing is possible
in this building for this particular climate. It also give a series of methods that can be
investigated to enhance night flushing’s performance or take a building that was not
designed for a certain passive feature and make it possible.

Figure 9.2.1 Final Main Reading Room Interior Temperature & PPD

9.3 – Potential Concerns
Night flushing is an effective passive and hybrid technology but it does not come
without flaws. A major issue with night flushing a one level library is the security issues
of opening operable windows at night. The thought of leaving windows open at night
makes the chance of the building being robbed a possibility. Ways to avoid such issues
would be to bar the windows from the inside. This is the most logical solution but
aesthetically it is not appealing and an architect would be unlikely to accept it. Another
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idea is to incorporate mesh screens around the opening. The flaw with a tight knit mesh
screen is that it restricts and slows down airflow. The ideal screen would be a metal
mesh with larger openings that do not impede air flow or allow too big of an opening for
intruders.
The opening size is also extremely important. The operable windows are
currently designed and were simulated for the opening to be 20°. The opening size helps
to reduce the amount of air entering the space as well as birds or other animals from
entering the library. The control of the airflow is extremely important because this is a
library with papers and books all around, too much airflow could end up knocking over
books and blowing around documents. Thomas Mayne and Morphosis Architects used
night flushing in the San Francisco Federal Building. The window openings were small
and the height of the building’s operable windows made human and animal intruders
improbable. For the Lakeview Terrace Library, the windows on the south side of the
Main Reading Room are 20 feet in the air so it makes it unlikely that they will be broken
in to. The windows on the north side are only three feet from the ground, so they
certainly would require the mesh screens. These strategies combined with a security
system should eliminate any reservations about security.
A potential concern about the night flushing simulation is the accuracy of a
simulation model. Right now, simulations are the best strategy for determining a
building’s thermal performance and potential energy consumption. But as you can see
from the EnergyPro simulation done for the library, simulations can only give a rough
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estimation and sometimes are not completely accurate. Another question about these
programs is which ones are the most accurate. If one program gives different results
than another then which one is correct? Energy programs use weather data that is
based on averages or prior weather; it can give a trend on what weather has done but
not on what it will do. What can be taken from this is that energy models and
simulations are a base case and give a rough estimation, but they are not a guaranteed
solution. Taking a simulation like this helps to understand how the building can perform
and the potential it has to succeed, but the only real way to see if something works is to
build a prototype or to find a similar case study. The strength of simulations is in its
ability to show the data and results within a program. Showing the improvement from
night flushing with improved thermal mass versus night flushing with improved thermal
mass and new glazing is a rational and accurate comparison. The numbers may not be
100% accurate but the data is proportional to a real life model.

9.4 – Overall Effectiveness of Night Flushing
This study shows that night flushing is effective for one particular building, but it
also reveals aspects of night flushing that need to be considered in any building design.
The role the climate plays is without a doubt the most valuable component of effective
night flushing. Regulations and climate standards must be met for natural conditioning
to even be a possibility. In order to night flush, extensive pre-design climate research
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needs to be performed. Wind studies, solar studies, temperature evaluations, and
humidity levels need to be understood.
The loads of a building need to be designed in coordination with the passive
cooling system. The effect internal and solar heat loads play on natural conditioning
determines whether or not a building is just too hot to be cooled by outdoor air. Night
flushing is much more than thermal mass and operable windows. It is orientation,
height, climate, funneling wind, heat capacity, lighting, exposed surfaces, computers,
equipment, people, humidity, indoor air quality, shading, glazing, and air velocity. Too
effectively night flush, a building has to work in synergy, all aspects and architectural
and engineering features affect each other. The main ideas to take from this study are
methods for making night flushing work, all of the aspects of climate and building design
that need to be considered, and how thermal comfort can be impacted by every
architectural and mechanical characteristic of a building.

9.5 – LEED Post - Occupancy
While the purpose of this study was to show how night flushing can be effective
and its impact on energy conservation, the real underlying theme was investigating a
LEED Platinum building and it faults. The idea of LEED certification is a badge of honor
for a building to show that it is green and sustainable. The idea that a building is
sustainable based on design ideas and simulations are far from being accurate. The
Lakeview Terrace Library is a perfect example of a building that was designed to use
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natural cooling with operable windows, thermal mass, and a state of the art evaporative
cooling tower and as it has been shown it does none of the above. LEED points are being
obtained to reach a certain level of prestige, being green is a way for a building to show
off. Just because a building displays its LEED Platinum plaque in the entrance of the
building that does not mean it is green. The Lakeview Terrace Library did not just
achieve LEED Platinum status because of its natural ventilation techniques. It met many
other requirements. But these two features stand out. The operable windows were
designed to cool the building and send a forced breeze into the courtyard. At this time
the windows are broken and do not open, and the door to get to the courtyard is locked
and the occupants of the library are not allowed to venture into the outdoor space.
The evaporative cooling tower was designed to use natural air to cool the lobby,
and it received innovative design points from LEED for it. At this point the tower has
never worked properly due to Bernoulli’s principle working in reverse, insufficient air
flow, and a broken water spraying system. This is clearly poor design, but the building
still achieved LEED points based on the theory of the tower, not its actual ability to
function. One of the caveats of the evaporative cooling tower receiving another point
needed to achieve LEED Platinum status was using the tower as a teaching tool by
displaying posters of its design at the foot of the tower. The library patrons can read
about how the tower works as they stand inside of it, while it in fact does not work.
A building only performs as effectively as its occupants allow it. Designing for
natural ventilation is great in theory, but if the occupants do not adhere to the
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guidelines that the system requires then it will never work. The problem with the library
is that the occupants have no problem with the buildings comfort level as it is. Air
conditioning is supplied throughout the summer and no one even realizes that the
natural cooling systems that were designed are not working.
What LEED needs is a post-occupancy evaluation system to ensure that a
building is actually performing the way its design received certification for. This would
put the onus on the owners, architects, engineers, and contractors to make sure a
system is designed and built correctly. If a post-occupancy evaluation was performed on
the Lakeview Terrace Library, it would lose its LEED Platinum accreditation. If there are
not any repercussions for a building not behaving like it received its certification for,
then by all means it should be reprimanded. In this case, Greenworks Studio designed
the tower and the operable window system and neither one work, and based on their
consulting and their energy model they received LEED credits. It is impossible for a
building to act exactly as the results an energy simulation has derived, but the library’s
annual energy consumes 40,000 kWh more than the simulation.
LEED is an instrumental tool for evaluating a building’s energy and
environmental designs and techniques. It sets the groundwork for designers to make
buildings that are better for the environment, but it needs to go beyond evaluating the
design and actually evaluate the constructed building. In Germany, the European Union
directive implemented an energy pass system in 2008 as an amendment to the Energy
Savings Act and the Energy Savings Ordnance (Energy Pass 2010). The energy pass
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system serves as an informative movement that is supposed to be an incentive for
energy conservation and modernization post-construction. The two variations of the
energy pass system used in Germany are the demand orientated and consumption
orientated energy passes. The demand orientated energy pass analyzes building
envelopes, materials, and heating to determine total heat loss to get a picture of a
building’s energy quality. The consumption orientated energy pass uses the heating and
cooling bills from the past three years to determine the energy consumption per square
meter. So there are currently systems that are in use to evaluate buildings post-
occupancy.
The Lakeview Terrace Library is just one example of a LEED building that is
flawed from its design. In order to really create a sustainable building, the architect,
engineers, contractors, owners, and the occupants need to work together t o achieve a
more carbon neutral building. If a design is engineered properly but is installed
incorrectly then the design is never fulfilled. A post – occupancy LEED system would be
extremely beneficial in making sure building’s carry through the idea of energy
efficiency and environmental design throughout a building’s life cycle whether it uses a
mechanical systems or a passive system like night flushing.

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Chapter 10: Areas for Future Research
The Lakeview Terrace Library proved to be a very interesting case study for
simulating the effectiveness and functionality of night flushing. There are still several
aspects of the library that need to be researched. The evaporative cooling tower was
rendered ineffective after it was constructed, and to this day it still is not operational.
Doing a study to completely understand why the tower is ineffective would be
extremely beneficial. The library claims that the tower is receiving insufficient air
velocity; why is this? Investigating how to redesign the tower is research that must be
done. It would appear that the Bernoulli principle from the air moving over the tower
would suck the wind up and out of the tower, not down it and into the building. The
pressure of the air moving past the tower would be higher than the air pressure at the
top of the tower. This “negatively pressured” space would cause air to be drawn out of
the space. It is the same idea as a door that opens into a building slamming shut on the
leeward side as wind is blowing by it. The library’s main natural feature is the
evaporative cooling tower, and as of now it is just a recognizable architectural feature.
There are posters and documentation on the library’s walls explaining the engineering
and design of the tower, without the occupants even realizing its not doing what it
claims. Ideas to consider for fixing the tower are its orientation, increasing air flow,
funneling wind, and mechanical assistance. The longer the tower’s openings are closed
and the water spraying mechanism is broken, the odds of the tower ever being fixed
continue to disappear. The occupants of the space are comfortable as is with air
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conditioning, and the cooling tower just does not seem to be a pressing issue.
The results of night flushing showed a significant decrease in the need for
mechanical cooling during the summer months, but in order to achieve this method of
effective natural ventilation it would be roughly a 19 year payback. Further tests can be
performed by trying different types of thermal mass materials. The shading was left as is
for the tests simulations of this study, methods to further reduce the solar gain in the
summer can be investigated. Other tests could be administered to find a less expensive
way to cool the building. The method could be testing and simulating a different mode
of natural conditioning or it could be introducing a new mechanical system like radiant
flooring or chilled beams. The thermal mass cost could be decreased and mechanical
fans can ventilate more cool night time air into the building.
The next issue in reducing the library’s energy consumption is reducing the
heating load and natural gas consumption. Now that the cooling load and energy
consumption has been considerably decreased, the heating load is consuming the
majority of the energy. In this study, in order for night flushing to be effective, the
shading coefficient was reduced so less solar gain enters the building in the summer but
it also decreases heat gain in the winter. Finding a way to reduce the heating load while
maintaining the newly designed night flushing is the next process in making this LEED
Platinum building an a actual sustainable building. A method for investigating this issue
would be examining the overhangs. The overhangs were left as is for this study, but
further investigation into the overhangs size and type would be a worthwhile study.
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Night flushing is typically ideal for southern California and desert climates,
comparing the results of night flushing in different climates would be a unique
investigation. Since night flushing is so climate dependent, it would be an interesting
study to take the library and put it in a different region of the world. This would give the
opportunity to see if the same architectural tweaks and tests would work there, or what
new methods and architectural enhancements would be needed based on climate.
This study was based on night flushing but it was also intended to further
investigate the LEED certification system and its lack of post occupancy evaluation.
Further studies into LEED would be extremely beneficial. Understanding why LEED labels
a building as an environmentally successful and energy efficient building based solely on
theory and design needs to be examined. Comparing a LEED Platinum building whose
main natural features are ineffective verse a non LEED building of the same square
footage and climate would be very interesting. If it was shown that their energy
consumption was similar, that knowledge and data would be a beneficial study.
When buildings are designed a certain way and they do not perform like they
were designed, it should be the architect and the engineers mission to understand why
and how to resolve the issue. Issues like these and what has happened with the
Lakeview Terrace Library are studies that need to be conducted to understand why
architectural engineering methods did not work and how to make sure these design
flaws do not occur in future buildings.

186

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191

Appendix A: Architectural Construction Drawings

Figure A.1 - LVT Floor Plan

Figure A.2 - LVT Roof Plan
192

Figure A.3 - LVT West Elevation

Figure A.4 - LVT South Elevation

Figure A.5 - LVT East Elevation

Figure A.6 - LVT North Elevation
193

Figure A.7 - LVT Section A-A

Figure A.8 - LVT Section B-B

Figure A.9 - LVT Section C-C

194

Figure A.10 - LVT Section D-D

Figure A.11 - LVT Section E-E

Figure A.12 - LVT Exterior Wall Section
195

Appendix B: HVAC Design Intent

Figure B.1 - Mechanical Plan

Figure B.2 - Chiller Schedule

Figure B.3 - Hot Water Boiler Schedule
196

Figure B.4 - Cooling Tower Evap. Unit Schedule

Figure B.5 - Fan Coil Schedule

197

Figure B.6 - Main Reading Room Fan Coil Control Diagram

Figure B.7 - Pump Schedule

198

Appendix C: Lakeview Terrace Solar Study

Figure C.1 - January 1
st
Solar Diagrams
199

Figure C.2 - February 1
st
Solar Diagrams

200

Figure C.3 - March 1
st
Solar Diagrams

201

Figure C.4 - April 15
st
Solar Diagrams

202

Figure C.5 - May 1
st
Solar Diagrams

203

Figure C.6 - June 1
st
Solar Diagrams

204

Figure C.7 - July 1
st
Solar Diagrams

205

Figure C.8 - August 1
st
Solar Diagrams

206

Figure C.9 - September 1
st
Solar Diagram

207

Figure C.10 - October 1
st
Solar Diagrams

208

Figure C.11 - November 1
st
Solar Diagrams

209

Figure C.12 - December 1
st
Solar Diagrams

210

Appendix D: Energy Management System Controls (EMSC)

Figure D.1 - EMSC Boiler Data

Figure D.2 - EMSC Chiller Data

211

Figure D.3 - EMSC Cooling Tower Data

Figure D.4 - EMSC Fan Coil Unit 1 Data
212

Figure D.5 - EMSC Fan Coil 2 Data

Figure D.6 - EMSC Fan Coil 3 Data
213

Figure D.7 - EMSC Fan Coil 4 Data

Figure D.8 - EMSC Fan Coil 5 Data
214

Figure D.9 - EMSC Fan Coil 6 Data

Figure D.10 - EMSC Fan Coil 7 Data
215

Figure D.11 - EMSC Fan Coil 8 Data

Figure D.12 - EMSC Fan Coil 9 Data
216

Figure D.13 - EMSC Chiller Schedule Figure D.14 - EMSC Master Schedule

217

Appendix E: Sylmar 2009 Weather Data for Cooling Months
2009 Annual Sylmar Weather Data
High Low Average
Temperature 105.3° F 33.1° F 66.1° F
Dew Point 66.8° F ¯ 2.2° F 38.8° F
Humidity 98.00% 4.0% 45.6%
Wind Speed 26.0 mph from the NW ¯ 3.5mph
Wind Gust 36.0 mph from the NW ¯ ¯
Wind ¯ ¯ South
Pressure 31.01 in 27.2 in ¯
Precipitation 10.67 in ¯ ¯

Figure E.1 - 2009 Annual Sylmar Weather Data

218

June 2009 Sylmar Weather Data
High Low Average
Temperature 104.1° F 53.4° F 69.5° F
Dew Point 62.9° F 24.2° F 51.9° F
Humidity 93.00% 8.0% 58.8%
Wind Speed 9.0 mph from the SW ¯ 3.2mph
Wind Gust 18.0 mph from the ENE ¯ ¯
Wind ¯ ¯ SSE
Pressure 28.70 in 28.38 in ¯
Precipitation 0.04 in ¯ ¯

Figure E.2 - June 2009 Sylmar Weather Data

219

July 2009 Sylmar Weather Data
High Low Average
Temperature 100.4° F 59.4° F 78.1° F
Dew Point 64.2° F 16.5° F 53.5° F
Humidity 88.00% 3.0% 41.6%
Wind Speed 9.0 mph from the SSE ¯ 2.7 mph
Wind Gust 15.0 mph from the SSE ¯ ¯
Wind ¯ ¯ SSE
Pressure 28.70 in 28.38 in ¯
Precipitation 0.0 in ¯ ¯

Figure E.3 - July 2009 Sylmar Weather Data

220

August 2009 Sylmar Weather Data
High Low Average
Temperature 99.8° F 60.3° F 78.4° F
Dew Point 64.2° F 16.1° F 54.7° F
Humidity 88.00% 5.0% 49.8%
Wind Speed 9.0 mph from the SSW ¯ 2.4 mph
Wind Gust 15.0 mph from the SE ¯ ¯
Wind ¯ ¯ SSE
Pressure 28.64 in 28.38 in ¯
Precipitation 0.0 in ¯ ¯

Figure E.4 - August 2009 Sylmar Weather Data

221

September 2009 Sylmar Weather Data
High Low Average
Temperature 99.4° F 57.2° F 76.1° F
Dew Point 64.2° F 16.4° F 49.2° F
Humidity 91.00% 6.0% 45.8%
Wind Speed 10.0 mph from the SW ¯ 2.5 mph
Wind Gust 15.0 mph from the SW ¯ ¯
Wind ¯ ¯ South
Pressure 28.70 in 28.41 in ¯
Precipitation 0.0 in ¯ ¯

Figure E.5 - September 2009 Sylmar Weather Data

222

Appendix F: Lakeview Terrace HOBO Data

Figure F.1 – HOBO 1
223

Figure F.2 – HOBO 2
224

Figure F.3 – HOBO 3

225

Figure F.4 – HOBO 4

226

Figure F.5 – HOBO 5

227

Figure F.6 – HOBO 6

228

Figure F.7 – HOBO 7
229

Figure F.8 – HOBO 8
230

Figure F.9 – HOBO 9

231

Figure F.10 – HOBO 10
232

Figure F.11 – HOBO 11

233

Figure F.12 – HOBO 12

234

Appendix G: Matching IES VE-Pro Model to Current Building Data
Fan Coil Unit 1 - The Main Reading Room – Section 1

Fan Coil Unit Service Total Sensible Cooling (BTUH) Ent. Air DB/WB
1 Main Reading 1– Teen 25600 79.9/67.1

Figure G.1 - FC-1 Cooling Load
235

Fan Coil Unit 2 – The Main Reading Room – Section 2

Fan Coil Unit Service Total Sensible Cooling (BTUH) Ent. Air DB/WB
2 Main Reading 2 32600 80.6/68.3

Figure G.2 - FC-2 Cooling Load

236

Fan Coil Unit 3 – Main Reading Room – Section 3

Fan Coil Unit Service Total Sensible Cooling (BTUH) Ent. Air DB/WB
3 Main Reading 3 32600 80.6/68.3

Figure G.3 - FC-3 Cooling Load

237

Fan Coil Unit 4 – Main Reading Room – Section 4

Fan Coil Unit Service Total Sensible Cooling (BTUH) Ent. Air DB/WB
4 Main Reading 4 32600 80.6/68.3

Figure G.4 - FC-4 Cooling Load

238

Fan Coil Unit 5 – Main Reading Room – Section 5

Fan Coil Unit Service Total Sensible Cooling (BTUH) Ent. Air DB/WB
5 Main Reading 5 26500 80.6/68.3

Figure G.5 - FC-5 Cooling Load

239

Fan Coil Unit 6 – Main Bookstacks, Electrical Room, & Mechanical Room

- VE-PRO
Fan Coil Unit Service Total Cooling Plant Sensible Load (BTUH)
6 Main Bookstacks, Elec. & Mech. Rms. 19478

- LVT Mechanical Schedule
Fan Coil Unit Service Total Sensible Cooling (BTUH) Ent. Air DB/WB
6 Main Bookstacks 26600 77.9/66
Figure G.6 – FC-6 Cooling Load

- Main Bookstacks

Figure G.7 - Main Bookstacks Cooling Load
240

- Electrical Room

Figure G.8 – Electrical Room Cooling Load

- Mechanical Room

Figure G.9 – Mechanical Room Cooling Load
241

Fan Coil Unit 7 – Staff Workroom, Lounge, Office, I.T. Room, Custodian, Storage, &
Restroom.

- VE-PRO
Fan Coil Unit Service Total Cooling Plant Sensible Load (BTUH)
7 Staff Workspaces 23759

- LVT Mechanical Schedule
Fan Coil Unit Service Total Sensible Cooling (BTUH) Ent. Air DB/WB
7 Staff Workrooms 24600 77.8/65.2
Figure G.10 - FC-7 Cooling Load

- Staff Workroom

Figure G.11 – Staff Workroom Cooling Load
242

- Staff Lounge

Figure G.12 – Staff Lounge Cooling Load

- Head Librarian Office

Figure G.13 – Head Librarian Office Cooling Load

243

- I.T. Room

Figure G.14 – I.T. Room Cooling Load

- Custodial Room

Figure G.15 – Custodial Room Cooling Load

244

- Staff Storage Room

Figure G.16 – Staff Storage Room Cooling Load

- Staff Restroom

Figure G.17 – Staff Restroom Cooling Load

245

Fan Coil Unit 8 – Multi-Purpose, Lobby, Restroom, Inactive Evaporative Cooling Tower,
Storage Room

- VE-PRO
Fan Coil Unit Service Total Cooling Plant Sensible Load (BTUH)
8 Multi-Purpose Room 62461

- LVT Mechanical Schedule
Fan Coil Unit Service Total Sensible Cooling (BTUH) Ent. Air DB/WB
8 Multi-Purpose Room 67200 88.6/69.7
Figure G.18 - FC-8 Cooling Load

- Multi-Purpose Room

Figure G.19 – Multi-Purpose Room Cooling Load

246

- Lobby

Figure G.20 - Lobby Cooling Load

- Main Restroom

Figure G.21 – Main Restroom Cooling Load

247

- Inactive Evaporative Cooling Tower

Figure G.22 – Cooling Tower Cooling Load

- Storage Room

Figure G.23 – Lobby Storage Room Cooling Load

Abstract (if available)

Abstract The goals of implementing natural cooling strategies are to reduce a building’s energy consumption, to improve the indoor climate, and to preserve natural resources. Energy preservation and sustainable design are beneficial for the building, its occupants, and the environment. When the passive technique of night flushing is used correctly with the appropriate architectural features, it can greatly reduce or eliminate the need for air conditioning and reduce peak energy demands. To test the efficiency of night flushing and to demonstrate its energy impact and its effect on building performance, the Lakeview Terrace library was chosen as a case study for modeling night flushing. The library is advertised as using night flushing for natural ventilation, but after investigating these claims it was discovered that the library was never designed to night flush. For this research, the library was modeled for night flushing in IES VE-Pro. After the building was modeled, its architectural features were altered to maximize energy efficiency by using night flushing. The simulations show the importance of internal and solar heat gain, as well as the role all of the building’s features play in natural ventilation. The results of this study demonstrated that the library redesigned with night flushing could drastically decrease its energy consumption while maintaining a comfortable indoor climate. It demonstrated that if the library would have been designed to naturally ventilate using night flushing, it could have greatly reduced the amount of energy needed for cooling as well as the cost to power its mechanical system. Night flushing offers an energy efficient alternative to HVAC without affecting the occupants’ comfort level.

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Asset Metadata

Creator Griffin, Kenneth A. (author)

Core Title Night flushing and thermal mass: maximizing natural ventilation for energy conservation through architectural features

School School of Architecture

Degree Master of Building Science

Degree Program Building Science

Publication Date 05/03/2010

Defense Date 04/23/2010

Publisher University of Southern California (original), University of Southern California. Libraries (digital)

Tag Lakeview Terrace Library,LEED post occupancy,mean radiant temperature,natural ventilation,night flushing,OAI-PMH Harvest,percentage of people dissatisfied,thermal comfort,thermal mass

Place Name California (states), Lakeview Terrace (city or populated place), Los Angeles (city or populated place), Santa Clarita (city or populated place)

Language English

Contributor Electronically uploaded by the author (provenance)

Advisor Noble, Douglas (committee chair), Kensek, Karen (committee member), Schiler, Marc (committee member), Simmonds, Peter (committee member)

Creator Email kagriffi@usc.edu,kennyg1221@gmail.com

Permanent Link (DOI) https://doi.org/10.25549/usctheses-m2985

Unique identifier UC1315042

Identifier etd-Griffin-3671 (filename),usctheses-m40 (legacy collection record id),usctheses-c127-314242 (legacy record id),usctheses-m2985 (legacy record id)

Legacy Identifier etd-Griffin-3671.pdf

Dmrecord 314242

Document Type Thesis

Rights Griffin, Kenneth A.

Type texts

Source University of Southern California (contributing entity), University of Southern California Dissertations and Theses (collection)

Repository Name Libraries, University of Southern California

Repository Location Los Angeles, California

Repository Email cisadmin@lib.usc.edu